33 


r.  S.  DEPARTMENT  OF  AGRICULTURE, 

BUREAU  OF  PLANT  INDUSTRY     BULLETINS.  193. 


li.  T.  GALLOWAY,  I  hi*)  ■■(  Bureau. 


EXPERIMENTS  IN  BLUEBERRY  CULTURE. 


BY 


FREDERICK  Y.  GOV1LLE, 
Botanist  in  Charge  op  Taxonomic  and  Range  In 


Issued  November  1">.  1910. 


r 


OOCUMpNTskfaj 


U.S.  OEPOSITORY 


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1910. 


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[Continued  on  page  3  of  cover.] 
1 9:; 


U.  S.  DEPARTMENT   (  >F   AGRIC1  fLTURE, 

BUREAU  OF  PLANT  INDUSTRY     BULLETIN  NO.  193. 

B.   I    GA1  LOWAY,  Chief  qf  Bureau. 


EXPERIMENTS  IN  l!LI  LltllltltY  CULTURE. 


FREDERICK  V.  COVILLE, 
Botanist  in  Charge  of  Taxon<  >mi«    vnd  Range  Investigations. 


[SSUBD    \<  IVEMBKR    15,    1910. 


WASHINGTON: 

GOVERNMENT     PRINTING     <  >l   I   !  C  E. 

L910. 


BUREAU  OF  PLANT  INDUSTRY. 


193 
2 


Chief  of  Bureau,  Bevekly  T.  Galloway. 
Assistant  Chief  of  Bureau,  G.  Harold  Powell. 
Editor,  J.   E.   Rockwell. 
Chief  Clerk,  James  E.  Jones. 


Taxonomic  and  Range  Investigations. 

scientific   staff. 

Frederick  V.  Coville,  Botanist  in  Charge. 
A.  S.  Hitchcock,  Systematic  Agrostologist. 
W.   F.   Wight,   Botanist. 
A.  II.  Moore  and  P.  L.  Ricker,  Assistant  Botanists. 

W.    E.    Safford,    Assistant    Curator. 
Agnes   Chase.   Assistant. 
E.  L.  Greene,   Expert. 


LETTER  OF  TRANSMITTAL. 


U.  S.  Depaei  \h  \ t  of  Agriculti  re, 

Bi  reai  or  Plant  I  ndi  stry, 

<  )i  i  H  e  of  the  Chief, 
Washington,  IK  C.,July  19,  1910. 

Sib:  I  have  the  honor  to  transmit  herewith  and  to  recommend  for 
publication  as  Bulletin  No.  L93  of  the  series  of  this  Bureau  a  manu- 
script by  Mr.  Frederick  V.  Coville,  Botanist  in  Charge  of  Taxonomic 
and  Range  Investigations,  entitled  "  Experiments  in  Blueberry  Cul- 
ture." Mr.  Coville  has  found  by  experiment  how  blueberries  differ 
from  ordinary  plants  in  their  method  of  nutrition  and  in  their  soil 
requirements,  and  by  means  of  this  knowledge  he  has  worked  out  a 
system  of  pot  culture  under  which  these  plants  attain  a  development 
beyond  all  previous  expectations.  There  is  good  prospect  that  the 
application  of  the  knowledge  thus  gained  will  establish  the  blue- 
berry in  field  culture  and  that  ultimately  improved  varieties  of  these 
plants  will  be  grown  successfully  on  a  commercial  scale. 

A  particularly  interesting  and  significant  feature  of  these  experi- 
ments is  the  light  they  shed  on  the  possible  utilization  of  the  natu- 
rally acid  lands  that  occupy  extensive  area-  in  the  eastern  United 
States.  These  land-  are  generally  valued  at  a  low  price,  and  the 
chief  expense  involved  in  their  utilization  for  ordinary  agricultural 
crops  is  the  cost  of  correcting  their  acidity  and  it-  effects  by  limine-. 
fertilizing,  ami  cultural  manipulation.     The  question  presents  itself, 

-  May  we  not  i v  effectively  utilize  such  land.-  by  growing  on  them 

crops  which,  like  the  blueberry,  thrive  in  acid  soil-?  '" 

Some  of  the  experimental  methods  and  equipment  utilized  by  Mr. 

Coville  are  commended  to  other  plant  experimenters,  especially  the 

f  darkened  and  drained  glass  pots  for  the  intimate  observation 

of  the  behavior  of  root-,  and  the  plunging  of  pots  in  moist  .-and  to 

maintain  equable  moisture  and  aeration  conditions. 

Respectfully, 

W  VI.    A  .    T  VYI.OK. 

Acting  Ck'u  i  of  Bun  <m. 
I  hiii.  James  Wilson, 

-  '/  of  .  Vgricultun  . 


Digitized  by  the  Internet  Archive 
in  2013 


http://archive.org/details/exinbluOOunit 


(  ONTENTS, 


I  in  mil  net  inn 11 

Peculiarities  of  growth  in  the  blueberry  plaut 14 

requirements 14 

i       swamp  blueberry  does  not  thrive  in  a  rich  garden  soil  of  the 
ordinary  type I  l 

(2)  Tli.-  -wain],  blueberry  does  not  thrive  in  a  heavily  manured  soil.        17 

(3)  The  swamp   blueberry  does  not  thrive  in  a  soil  made  sweet  by 

lime lit 

(4)  The  swamp  blueberrj  does  not  thrive  in  a  heavy  clay  soil 24 

(5)  The  swamp  blueberry  does  not  thrive  in  a  thoroughly  decomposed 

leal  mold,  such  as  lias  a  neutral  reaction 24 

(6)  The  swamp  blueberry  does  not  thrive  in  Boils  having  a  neutral  or 

alkaline  reaction,  hut  for  vigorous  growth  it  requires  an  acid 

soil 26 

(7)  The  favorite  type  of  acid  soil  for  the  swamp  blueberry  is  peat. . .        -ii 

(8)  l'eat  suitable  for  the  swamp  blueberry  may  be  found  either  in 

bogs  or  on  the  surface  of  the  ground  in  sandy  oak  or  pine  w Is.        32 

(9)  For  active  growth  the  swamp  blueberry  requires  a  well-aerated 

soil.      Conversely,  the  swamp  blueberry  dees   not    continue   in 

acti\  e  grow  th  in  a  soil  saturated  with  water :'.-"> 

(10)  Aeration   conditions  satisfactory  for  the  swamp  blueberry  are 

prevalent  in  s  Is 36 

(11)  Aeration  condition-  satisfactory  for  the  swamp  blueberry  are 

found  in  drained  fibrous  peat 37 

deration   conditions  satisfactory    for  the  swamp  blueberry  are 
found  in  masses  of  live,  moist,  hut  nol  submerged,  sphagnum..        38 

Peculiarities  of  nutrition 40 

13)  The  swamp  is  devoid  of  root  hairs,  tic  minuti 

through  which  the  ordinary  planl  ulture  absorb  their 

moisture  and  f 1 40 

(14)  Tlr  of  healthy  plant- of  the  swamp  blueberry  are  in- 

habited by  a  fungus,  of  the  sort  known  technically  as  an  endo- 

trophic  mycorrhiza 42 

(  15)  The  mycorrhiza]  fungus  of  the  swamp  blueberry  appears  to  have 
no  injurious  effect,  hut  rather  a   beneficial  effect,  upon    the 

blueberry  plant 44 

The  acid  peaty  soils  in  which  the  swamp  blueberry  thrives  are 
deficient   in  "available"  nitrogen,  although  containing  lar^e 

amount-  of  "nonavailable"  nitrogen 45 

(17)  The  deficienc}  oi  available  nitrogen  in  the  acid  peaty  -oil  in 
which  the  swamp  blueberry  grows  besl  is  d  ie  to  tl  e  inability 
of  the  nitrifying  ba<  teria  to  thrive  in  such  a  -oil  because  of  it- 

acidity  46 

193 


CONTENTS. 


Peculiarities  of  growth  in  the  blueberry  plant- 
Peculiarities  of  nutrition — Continued . 


-Continued. 


(18 

(19 

A  method  of 
(20 

(21 

(22 
(23 
(24 

(25 

(26 

(27 

(28 

(29 

(30 
(31 
(32 


(33 

(34 

(35 
(36 

l!.:; 


Page. 


From  the  e\  idence  at  hand  the  presumption  is  that  the  mycor- 
rliizal  fungus  of  the  swamp  blueberry  transforms  the  nonavail- 
able  nitrogen  of  peaty  soils  into  a  form  of  nitrogen  available 
for  the  nourishment  of  the  blueberry  plant 48 

It  is  possible  that  the  mycorrhizal  fungus  of  the  swamp  blue- 
berry transforms  the  free  nitrogen  of  the  atmosphere  into  a 
form  of  nitrogen  suited  to  the  use  of  the  blueberry  plant 48 

pot  culture 51 

Seeds  of  the  swamp  blueberry  sown  in  August  from  fresh  berries 
germinate  in  about  5  weeks 51 

The  seedlings  are  first  transplanted  at  the  age  of  about  6  weeks, 

when  they  are  approaching  an  inch  in  height 54 

When  about  10  weeks  old  and  nearly  2  inches  in  height  the 
seedlings  1  legin  to  send  out  basal  branches 57 

When  the  seedlings  are  about  4  months  old  and  about  3  inches 
in  height  the  growth  of  the  original  stem  terminates 58 

When  the  plants  are  about  5  months  old  and  4  to  6  inches  in 
height  they  are  potted  in  4-inch  pots  in  the  best  peat  or  prat 
mixture 59 

Blueberry  plants  potted  in  peat  may  be  made  to  grow  more  rap- 
idly if  they  are  watered  occasionally  during  the  growing  season 
with  water  from  a  manure  pit 62 

Pots  containing  blueberry  plants  should  be  plunged  in  sand  or 
other  material  that  will  furnish  constant  moisture  and  gi  ol 
aeration 65 

Plants  of  the  swamp  blueberry  sometimes  lay  down  flowering 
buds  at  the  age  of  7  months 67 

In  the  spring  after  the  danger  of  frost  was  past  the  plants  were 
repotted  and  placed  out  of  doors,  in  half  shade,  plunged  in 
sand 67 

By  the  use  of  the  cultural  methods  already  described,  seedlings 
of  the  swamp  blueberry  have  been  grown  into  robusl  plants 
of  a  maximum  heighl  of  27  inches  at  12  months  from  germi- 
nation          68 

The  (lowering  buds  of  the  blueberry  are  produced  by  the  trans- 
formation of  dormant  leaf  buds  in  the  latter  pari  of  the  season.  71 

At  the  end  of  their  first  year  70  per  cent  of  the  blueberry  plants 
had  laid  down  flowering  buds  for  the  next  spring's  blossoming.        73 

Plants  of  the  swamp  blueberry  are  exceedingly  hardy  and  pass 
the  winter  in  good  condition  outdoors  when  the  soil  is  covered 
merely  with  an  oak-leaf  mulch,  but  when  not  exposed  to  out- 
door  ei  i  ml  it  ions  they  do  not  begin  their  growth  in  spring  in  a 
normal  manner 74 

Dormant  plants  make  their  early  spring  twig  growth  before  new 
roots  begin  to  develop 76 

Unless  pollinated  by  an  outside  agency,  such  as  insects,  the 
Sowers  produce  little  or  no  fruit 76 

The  f i  nit  matures  aboul   2  months  after  the  flowering 78 

So  far  as  observed,  the  swamp  blueberry  when  grown  in  acid 

soils  is  little  subject  to  fungous  diseases  or  insect  pests 79 


C0N1  ENTS.  7 

Improvement  and  propagation 80 

.•hi  plant  of  the  swainp  blueberry  seedlings,  the  culture 
of  which  has  been  described,  bore  berries  over  hall'  an  inch  in 

diameter 80 

There   is  every  reason   to  believe    that    the   blueberry  can  bi 

improved  by  breeding  and  l>y  selection 82 

The  swamp  blueberry  bas  been  propagated  by  grafting,  by  bud- 
ding, by  layering,  by  twig  cuttings,  and  by  root  cuttings 83 

sirable  method  of  propagating  the  swamp  blueberry 

is  by  cuttings 84 

Field  culture 36 

;  leriments  have  been  begun  in  the  field  culture  of  the  swamp 

blueberry ^ 86 

Conclusion 38 

Index  9] 


ILLUSTRATIONS 


PLATES. 

Page 
Plate  I.   Fig.   1. — Rool  growth  of  a  blueberry  plant  in  clay  mulched  with 

leavi  2      Ri  o1  growth  of  a  blueberry  plant  in  peat lM 

1 1.   Blueberry  Beedlings  in  prat  and  leaf  mold 26 

III.  Fig    I       Formation  of  kalmia  prat,  top  layer.     Fig.  2. — Formation 

of  kalmia  prat,  second  layer 

IV.  Fig.  L. — Formation  of  kalmia  peat,  third  layer.     Fig.  2.     Formation 

of  kalmia  peat,  fourth  layer 34 

Y.   Fig.  1. — Formation  of  kalmia  peat,  fifth  layer.     Fie.  2. — Formation 

of  Kalmia  pi 'at,  sixth  lay  it 34 

VI.   Fig.  1. — Swamp  blueberries  from  the  parent  bush  of  the  seedlings < 

1908.     Fig.  2.     Seeds  of  the  swamp  blueberry 52 

VII.   Blueberry  seedling  four  and  a  half  months  old 60 

VIII.  Cold  frames  containing  one-year-old  blueberry  seedlings 68 

1  \.   Large  one-year-old  seedlings  of  the  swamp  blueberry 70 

X.   Fig.   1.     Flowering  buds  and  leaf  buds  on  blueberry  twigs.     Fig.  2. 
Flowering  buds  <>n  a  blueberry  cutting.     Fig.  :>. —  Flowering  buds 

on  blueberr}  cuttings ~i. 

XI.   Yearling  blueberry  plant  with  -1'-'  flowering  buds 74 

XII.  I"i(..  l.  Blueberry  plant  which  wan  wintered  indoors  beginning 
growth  in  the  spring.  Fig.  2.  —  Blueberry  plant  which  was  win- 
ten.  1  outdoors  beginning  growth  in  the  sprint: 76 

\1II  I  :  i  Blueberry  plant  which  was  wintered  indoors  continuing 
growth  in  the  spring.  Fig.  2.  —  Blueberry  plant  which  was  win- 
tered outdoors  continuing  growth  in  the  spring 7'> 

XIV.   Irregular  flowering  ol  a  blueberry  plant  wintered  indoors 78 

X  V.  I  Jerry  ripened  on  a  blueberry  seedling  at  the  age  of  19  months s" 

XVI.  Fig.  l.  Grafted  blueberry.  Fig.  -.  Blueberry  seedling  success- 
fully budded 84 

XVII.   Blueberry  plants  from  twig  cuttings 86 

XVIII.   Blueberry  plant  from  a  twig  cutting ^ 

[•EXT    lie 

lie      i .   Rose  cutting  in  rich  garden  soil 16 

Rose  cutting  in  peat  mixture 

Alfalfa  seedlings  in  rich  garden  soil 17 

i     Alfalfa  seedlings  in  peal  mixture 17 

5    Blueberr)  seedling  in  rich  garden  soil 18 

ng  in  peat  mixture 18 

7.   Blueberry  seedling  in  peat  mixture  limed 23 

-    Blu<  berry  seedling  in  peat  mixture  tin  lime.  I 23 

9.   Blueberry  seedling  fed  with  alkaline  nutrient  solution 

10.   Blueberry  seedling  fed  with  acid  nutrient  solution :il 

193  ., 


10  ILLUSTRATIONS. 

Page. 

Fig.  11.  Root  of  a  wheat  plant,  showing  the  root  hairs 40 

12.  Portion  of  a  wheat  root,  with  root  hairs 40 

13.  Tip  of  the  root  hair  of  a  wheat  plant 40 

14.  Root  of  a  blueberry  plant 41 

15.  Root  of  a  blueberry  plant,  enlarged 41 

16.  Blueberry  rootlet 41 

17.  Mycorrhizal  fungus  of  a  blueberry  plant   densely  crowded  in  two 

epidermal  cells  of  the  root 43 

18.  Mycorrhizal  fungus  of  Kalmia  latifolia  in  an  epidermal  cell  of  the  root.  44 

19.  Section  of  a  blueberry  seed 53 

20.  Blueberry  seedlings  in  the  cotyledon  stage 53 

21.  Blueberry  seedling  about  6  weeks  old,  with  five  foliage  leaves 54 

22.  Normal  tip  of  stem  in  a  blueberry  seedling 57 

23.  Bract  and  young  leaf  at  the  end  of  the  original  stem  in  a  blueberry 

seedling 58 

24.  Blueberry  seedling  with  diffuse  type  of  branching 59 

25.  Blueberry  seedling  of  the  type  with  few  branches 59 

26.  Spores  of  a  supposedly  injurious  fungus  in  the  epidermal  cells  of  blue- 

berry roots 64 

27.  Flowers  of  the  blueberry,  from  1908  seedlings  of  the  large-berried 

New  Hampshire  bush  of  Vaccinium  corymbosum 77 

28.  Stamens  of  the  blueberry 77 

29.  Compound  pollen  grain  of  the  blueberry 78 

30.  Pistil  and  calyx  of  the  blueberry,  showing  the  style  and  stigma 78 

31.  Blueberry  plant  grown  from  a  root  cutting 86 

193 


B.  r    i 


EXPERIMENTS  IN  BLUEBERRY  CULTURE. 


INTRODUCTION. 

Iii  the  grounds  of  the  Smithsonian  [nstitution  at  Washington  are 
two  blueberry  bushes  of  large  size  and  great  age.  The  taller  is  about 
9  feel  high.  The  largesl  stem  is  nearly  3  indies  in  diameter.  It  is 
known  that  these  bushes  v\  ere  growing  prior  to  L871,  thirty-nine  years 
ago,  and  all  the  evidence  indicates  that  they  were  planted  at  a  much 
earlier  date.  They  are  probably  over  50  years  old."  In  the  Arnold 
Arboretum,  near  Boston,  are  many  blueberry  bushes  30  years  old 
or  more,  grown  from  the  ^^l  by  Mr.  Jackson  Dawson  or  trans- 
planted from  their  wild  habitats  prior  to  L880. 

The  two  cases  here  cited  demonstrate  the  fallacy  of  the  popular 
idea  that  the  blueberry  can  not  lie  transplanted  or  cultivated.  This 
idea  rot-  on  the  unsuccessful  experience  id'  those  who  have  taken  up 
wild  bushes  and  -et  them  in  a  rich,  well-manured  garden  soil.  These 
air  exactly  the  condition-,  as  shown  by  experiment-  described  in  this 
publication,  under  which  blueberry  plant-  become  feeble  and  unpro- 
ductive. 

four  agricultural  experiment  stations,  those  of  Maine.  Rhode 
[sland,  New  York,  and  Michigan,  have  attempted  to  grow  the  blue- 
berry a-  a  fruit,  hut  none  of  these  attempts  ha-  resulted  in  the  com- 
mercial success  "f  blueberry  culture,  and  the  experimental  results 
have  boen  chiefly  of  a  negative  character.  This  outcome  appear-  to 
have  been  *\\\r  to  a  misunderstanding  of  the  soil  requirements  of  the 
blueberry,  which,  as  will  be  shown  later,  are  radically  different  from 
those  of  our  common  cultivated  plan-. 

"  The  plants  are  i  actinium  atrococcum,  n  species  closely  related  to  Vactinium 
corymbosum,  the  well-known  swamp  or  high  hush  blueberry  of  the  Northern 
Stales,  lu  a  list  of  the  trees  ami  shruhs  of  the  Smithsonian  grounds  prepared 
by  Arthur  Schotl  in  ls~l.  these  bushes  are  included,  but  identified,  ho\  ■  i 
as  Vavcinium  fuscatum.  The  hue  Mr.  George  II.  Brown,  for  mere  than  a  gen- 
eration the  superintendent  of  planting  in  the  parks  of  Washington,  also  as- 
sured the  waiter  that  these  plants  were  not  set  out  since  he  first  became 
responsible  for  the  Smithsonian  grounds,  in  1871.  The  present  plan  of  the 
grounds  was  made  by  Mr.  Andrew  J.  Downing,  bul  the  actual  planting  was  not 
done  until  after  his  death,  in  1852.  It  is  possible  thai  the  blueberry  hushes 
may  have  been  set  eat  as  early  as  1848,  in  whicb  year  a  partial  planting  of  the 

Smithsonian  grounds  was  made  by  Mr.  John  I glass. 

L93  11 


12 


EXPERIMENTS  IN  BLUEBERRY  CULTURE. 


In  the  Boston  market  there  is  a  wide  variation  in  the  wholesale 
price  of  blueberries.  Shipments  begin  in  early  June  from  North 
Carolina,  followed  in  the  hitter  part  of  the  month  by  blueberries  from 
Pennsylvania,  New  Jersey,  and  New  York.  In  early  July,  or  in 
some  years  in  the  last  days  of  June,  Massachusetts  and  New  Hamp- 
shire shipments  begin  to  arrive,  succeeded  in  late  July  or  early 
August  by  berries  from  Maine,  Nova  Scotia,  and  New  Brunswick. 
Receipts  from  these  last  two  localities  continue  until  late  September. 
The  blueberries  that  bring  the  highest  price  are  those  from  Massa- 
chusetts and  New  Hampshire.  At  the  time  when  other  berries  are 
selling  at  8  to  15  cents  per  quart  wholesale,  the  first  shipments  of 
New  Hampshire  berries  often  bring  20  to  23  cents. 

The  owner  of  a  blueberry  pasture  in  southern  New  Hampshire 
who  superintended  the  picking  of  his  own  berries  and  shipped 
them  to  one  of  the  secondary  New  England  cities  has  courteously 
shown  his  shij^ment  records,  from  which  the  following  data  have 
been  compiled : 


Records  of  shipments  from  n  blueberry  pasture  in  southern  New  Hampshire, 

1905-1909. 


Year. 

Date  of  shipment. 

Total 
ship- 
ments. 

Highest  iuhI 
lowest  price 

per  quart." 

Average 
price  per 
quart,  a 

1905 

July  1  to  Aug.  14 

July  20  to  Aug.  15.... 

June  29  to  Aug.  15 

July  15  to  Aug.  16 

Quarts. 
2,233 

2,756 
2,538 
3, 602 

l , .'.  B 

Cents. 
12i  to   8 

15  to   8 

14J  to  11 

16  to    9± 
11    to    9 

i  'eats. 
10.7 

1906 

9.6 

1907...                             

12.2 

1908 

10.8 

1909 

10.7 

a  This  is  the  net  price  that  the  shipper  received  after  deducting  express  charges. 

The  average  net  price  for  the  five  years  was  10.8  cents  per  quart. 
The  record  indicates  the  substantial  returns  that  arc  secured  from 
ordinary  wild  berries  picked  and  sent  to  market  in  rather  better  than 
ordinary  condition. 

That  the  market  would  gladly  pay  a  high  price  for  a  cultivated 
blueberry  of  superior  quality  there  can  be  no  doubt.  From  the 
market  standpoint  the  featui'es  of  superiority  in  a  blueberry  are  large 
size;  light-blue  color,  due  to  the  presence  of  a  dense  bloom  over  the 
dark-purple  or  almost  black  skin:  "dryness,"  or  freedom  from  super- 
ficial moisture,  especially  the  fermenting  juice  of  broken  berries; 
and  plumpness,  that  is.  freedom  from  the  withered  or  wrinkled  ap- 
pearance that  the  berries  begin  to  acquire  several  days  after  picking. 
While  the  connoisseur  in  blueberries  who  picks  his  own  fruit  knows 
the  widely  varying  flavors  in  the  berries  of  different  bushes,  the  buyer 
in  the  city  market  is  content  to  select  his  fruit  according  to  its  ap- 
pearance, knowing  that  the  flavor  will  be  good  enough  in  any  event. 

193 


I  111.    PICKING    "l     l.l.i   il-.i  RKIES.  13 

The  size  of  the  seed  gives  the  buyer  in  Xew  England  markets  verj 
little  concern,  for  there  the  name  bluebern  is  restricted  to  plant-  of 
the  genus  Vaccinium,  all  of  \\  hich  have  seeds  so  small  as  to  be  unno- 
ticeablewhen  the  berry  is  eaten,  while  the  name  huckleberry  is  applied 
with  nearly  the  same  precision  to  the  species  of  the  genus  Gaylus- 
sacia,  in  which  the  seed  is  surrounded  by  a  bonj  covering  like  a 
minute  peach  pit,  which  crackles  between  the  teeth.  In  -out hern  cities 
the  fruits  of  both  Vaccinium  and  Gaylussacia  arc  called  huckleberries, 
and  it  is  probable  that  the  low  estimation  in  which  the  fruit  of  Vac- 
cinium is  there  held  is  largely  due  to  the  lack  of  a  distinctive  popular 
name.  To  distinguish  the  two  berries  by  their  appearance  is  difficult 
for  any  but  an  expert,  for  while  huckleberries  are  mostly  black  and 
blueberries  mostly  blue,  some  of  the  blueberries,  or  species  of  Vac- 
cinium, are  black,  and  -nine  of  the  huckleberries  are  blue,  notably 
frondosa,  a  species  often  abundant  in  the  sandy  soils  of 
the  Atlantic  Coastal  Plain,  which  has  a  large,  handsome  berry  of  a 
beautiful  light-blue  color  and  passable  flavor,  but  with  the  disagree- 
ably crackling  seed  pit-  characteristic  of  the  other  true  huckleberries. 

The  blueberry  withstands  the  rough  treatment  incident  to  ship- 
ment so  much  better  than  most  other  berries  that  with  proper  han- 
dling it  should  always  reach  the  market  in  first-class  condition. 
Bui  ii-  good  shipping  qualities  are  often  abused,  and  the  fruit  not 
infrequently  is  exposed  for  sale  partly  crushed  and  the  berries  cov- 
ered with  soured  juice  and  made  further  offensive  by  the  presence  of 
flies.  This  is  the  prevailing  condition  of  blueberries  and  huckle- 
berries in  the  market-  of  Washington,  in  striking  contrast  with  the 
dry,  plump  berries  of  the  Boston  market.  This  had  condition  i-  due 
usually  to  improper  picking. 

The  small  size  of  the  blueberry,  compared  with  other  berries,  ren- 
ders the  picking  of  it  expensive.  The  owner-  of  blueberry  pastures 
commonly  pay  two-third-  the  net  price  of  the  berries  to  their  pickers. 
In  order  to  reduce  the  cost  of  picking,  various  devices  have  b< 
employed.  The  mosl  widely  \\-^^\  of  these  is  an  implement  known 
as  a  blueberry  rake,  a  scoop  shaped  somewhat  like  a  deep  dustpan, 
provided  in  front  with  a  series  of  long,  pointed  fingers  of  heavy  wire. 
With  this  implement  an  ordinary  picker  in  the  blueberry  canning 
districts  of  Maine,  for  example,  gathers  •">  to  ■>  bushels  a  day.  for 
which  he  receives  l  .  to  •_'  cent-  per  quart.  Blueberries  can  he  picked 
with  a  rake  at  about  a  fourth  the  cost  of  picking  by  hand.  For  this 
reason  many  of  the  berries  that  go  to  market  are  picked  with  a 
rake,  and  it  i-  these  berries  which,  broken  and  fermenting,  make 
up  the  greater  part  of  the  low-grade  stock  so  offensive  to  the  eye 
and  the  ta-te.  Blueberries  intended  for  the  market  should  never  he 
picked  with  a  rake. 
193 


14  EXPERIMENTS   IN   BLUEBERRY   CULTURE. 

What  has  been  said  regarding  the  high  cost  of  picking  ordinary 
blueberries  by  hand  indicates  the  importance  of  securing  a  berry  of 
large  size  if  the  plant  is  to  be  cultivated.  Large  size  and  abundance 
mean  a  great  reduction  in  the  cost  of  picking.  Large  size  mean- 
also  a  higher  market  price,  and  when  taken  in  connection  with  good 
color  and  good  market  condition  it  means  a  much  higher  price. 

The  writer's  interest  was  attracted  to  the  subject  of  blueberry  cul- 
ture in  1906.  In  the  autumn  of  that  year  some  experiments  were 
made  for  him  by  Mr.  George  W.  Oliver  to  ascertain  a  suitable  method 
of  germinating  the  seeds.  In  the  autumn  of  1907  special  cultural  ex- 
periments were  taken  up.  In  1908  experiments  were  begun  in  the 
propagation  of  bushes  bearing  berries  of  large  size,  the  most  satis- 
factory of  these  being  a  New  Hampshire  bush  of  the  swamp  blueberry 
{Vaccinium  corymbosum)  having  berries  a  little  more  than  half  an 
inch  in  diameter.  The  largest  berries  tried,  a  little  more  than  five- 
eighths  of  an  inch  in  diameter,  were  from  Oregon  bushes  of  Vac- 
cinium membranaceum.  Except  where  otherwise  stated,  the  experi- 
ments described  in  this  paper  were  made  with  Vaccinium  corym- 
bosum: The  principal  results  of  the  experiments  are  given  under 
brief  numbered  statements,  each  followed  by  a  detailed  explanation. 

PECULIARITIES   OF    GROWTH   IN    THE   BLUEBERRY   PLANT. 

soil  requirements. 

(1)  The  swamp  blueberry  does  not  thrive  in  a  rich  garden  soil  of  the 
ordinary  type. 

Although  the  statement  just  made  might  well  rest  on  the  direct 
observation  of  experimenters  who  have  failed  to  make  blueberries 
grow  luxuriantly,  or  sometimes  even  remain  alive,  in  rich  garden 
soils,  nevertheless  the  citation  of  one  of  the  writer's  experiments  may 
serve  to  accentuate  the  fact.  The  soil  chosen  for  the  purpose  was  the 
one  used  at  the  United  States  Department  of  Agriculture  for  grow- 
ing roses.  A  sample  of  this  soil,  as  mixed  by  the  rose  gardener,  con- 
sisted, according  to  his  specifications,  of  "  five  shovelfuls  of  loam,  one 
shovelful  of  cow  manure,  and  a  handful  of  lime."  The  loam  used 
was  a  rotted  grass  turf  grown  on  a  rather  clayey  soil.  The  cow 
manure  was  well  rotted,  having  lain  in  the  pile  for  several  months, 
with  almost  no  admixture  of  straw.  The  lime  was  of  the  ordinary 
air-slaked  sort. 

The  pots  used  in  the  experiment  were  of  glass,  small  5-ounce  drink- 
ing glasses,  about  2  inches  in  diameter  at  the  bottom,  2.1  at  the  top, 
and  L;:;  inches  dee]).  A  small  hole  bored  through  the  bottom  gave  the 
necessary  drainage  t<>  the  -nil  in  the  pot.  Since  the  walls  of  these 
pots  were  transparent,  the  normal  growth  of  the  roots  and  the  pre- 


THE    USE   OF   GLASS    POl  3.  15 

vention  of  an  obscuring  green  growth  of  microscopic  algse  required 
some  arrangement  for  keeping  the  light  away.  This  was  accom- 
plished cither  by  sinking,  or,  as  gardeners  say,  "  plunging,"  the  pots 
nearly  to  the  rim  in  sand,  moss,  or  soil,  or,  when  the  pots  were  nol 
plunged,  by  fitting  closely  to  the  outside  of  each  a  removable  cuff,  as 
it  were,  made  of  the  opaque  gray  blotting  paper  used  in  pressing 
specimens  of  plant-.  The  use  of  a  pot  with  transparent  walls  was 
found  to  l>e  of  \  ery  great  importance  in  the  st  udy  of  these  plants-,  for 
plant-  identical  in  appearance  SO  far  a-  the  parts  above  ground  were 
concerned  sometimes  showed  the  most  pronounced  differences  in  the 
growth  ami  behavior  of  the  rout-,  differences  which  otherwise  would 
not  have  been  observed  but  which  were  in  reality  responsible  for  the 
conspicuous  changes  that  later  took  place  in  the  growth  of  the  -tem< 
and  leave-.  The  use  of  such  glass  pot-,  drained  and  darkened,  t- 
strongly  recommended  to  plant  experimenters  who  use  pot  cultures, 
as  they  afford  a  mean-  of  acquiring  easily  an  intimate  knowledge  of 
_reat  variation-  in  the  behavior  of  the  feeding  organs,  the  roots, 
under  di  fferent   condit  ions. 

On  December  •_'•_'.  L908,  six  glass  pot-  were  tilled  with  the  garden 
-oil  described  above,  and  a  seedling  blueberry  about  an  inch  in  height 
was  transplanted  into  each.  The  -fn\  bed  from  which,  the  seedlings 
were  taken  had  been  allowed  to  become  partially  dry  before  the 
transplanting  was  done.  In  this  condition  there  was  no  difficulty  in 
removing  all  of  the  sandy  -oil  adhering  to  the  roots  of  a  seedlii 
that  after  it  wa-  transplanted  it  must  derive  it-  -oil  nourishment 
from  the  new  soil  exclusively.  In  potting,  the  root-  of  the  plant 
were  laid  against  the  jilass  on  one  side  of  the  pot  -o  that  their 
behavior  could  he  observed  from  the  very  first. 

\  transplanting  of  six  other  plant-  was  then  made,  similar  in  all 
respects  to  the  first  except  that  the  soil  used  was  a  peat  mixture  known 
from  earlier  experiment-  to  he  productive  of  rigorous  growth  in 
blueberry  plant.-.  The  exact  character  of  this  -oil  will  he  discussed 
later  in  this  publication. 

Tin-  peaty  blueberry  -oil  i-  ill  suited  to  the  growth  of  ordinary 
plant.-,  while  in  the  garden  soil  ordinary  plants  flourish  luxuriantly. 
I  n  order  to  bring  out  this  fact  clearly  by  an  experiment  six  glass  pots 
containing  this  garden  -oil  were  planted  with  live  alfalfa  -ceil-  each. 
and  six  more  with  one  rooted  rose  cutting  each.  An  identical 
planting  was  made  in  twelve  pots  of  blueberry  soil. 

A.verage  example-  of  the  growth  that  took  place  in  these  plantings 
arc  shown  in  figures  I  to  6,  reproduced  from  drawings  carefully  made 
from  actual  photographs.  In  the  garden  soil  the  rooted  rose  cut- 
ting, which  wa-  of  the  variety  known  a-  Cardinal,  made  vigorous 
growth  of  both  root  and  stem,  and  in  forty-four  day-,  when  the 
I  a:; 


16 


EXPERIMENTS   IN    BLUEBERRY    CULTURE. 


photograph  was  taken,  had  about  quadrupled  its  leaf  surface.  In  the 
blueberry  soil  the  cutting  was  barely  alive1,  the  roots  it  had  at  the 
time  it  was  potted  were  nearly  all  dead,  no  new  stem  growth  had  been 
made  and  the  leaflets  it  bore  were  only  those  still  persisting  from 
the  parent  plant. 

The  alfalfa  seeds  began  to  germinate  in  both  soils  in  three  days. 
At  the  end  of  a  week  a  distinct  difference  in  the  color  of  the  plants 
was  discernible.  In  the  blueberry  soil  the  seed  leaves  were  darker 
green  in  color,  the  midrib,  which  shows  on  the  back  of  the  leaf,  was 


!  [g.   I.-  Roso  cutting  in  rich  garden  soil. 
1 1  >ne  ba  1 1  na  i  ura  I  size,  i 


Fn    2      Rose  cutting  in  peal  mix- 
ture.     (One  half  natural  size. 


purple,  the  stem  was  purple,  and  in  some  of  the  seed  leaves  the  whole 
under  surface  was  purple.  In  the  garden  soil  the  seed  leave-  were 
lighter  green  in  color,  and  in  only  a  few  were  the  stems,  and  in  -till 
fewer  the  midribs,  some\*  hat  purplish.  At  the  end  of  forty-four  days, 
when  the  photographs  reproduced  in  figures  3  and  A  were  taken,  the 
alfalfa  plants  in  the  garden  soil  were  3  inches  in  height  and  vigorous, 
while  lie  -oil  was  crowded  with  roots  on  which  nitrogen  tubercles 
had  already  begun  to  develop.  In  the  blueberry  -oil  the  plant-  were 
small  leaved  and  sickly,  about  a  third  the  height  of  the  other-,  and 
193 


I  N.I  I   RI01   -    EFFEl    is   OF    lilCIl    GARDEN    SOIL. 


IT 


the  roots  though  long  were  slender  and  otherwise  weak  and  bore  no 
tubercles. 

In  the  case  of  the  blueberry  plants  the  relative  growth  in  the  two 
-nil-  took  exactly  the  opposite  course.  At  the  end  of  the  first  week  new 
root  growth  had  begun  in  all  the  pots  containing  blueberry  soil,  while 
in  those  containing  garden  -oil  new  root  growth  was  apparenl  in  only 
one.  At  the  end  of  forty-four  days  vigorous  rool  growth  had  taken 
place  in  the  blueberry  soil  pots,  and  stem  growth,  which  had  been 
interrupted  at  the  time  of  transplanting,  was  well  under  way  again. 
In  the  garden  soil,  however,  almost  no  root  growth  was  discernible, 

il Id  leaves  were  strongly  put-pled  and  stem  and  leaf  growth  had 

nol  been  resumed.    Little  attention  was  paid  to  these  culture-  during 
the  summer  of  L909,  but  the  relative  condition  of  the  two  is  fairly 


Fig.  3. — Alfalfn  seedlings  In  rich  garden  soli.      Fio.  4. — Alfalfa  seedlings  In  peat   mixture. 
I  natural  size,  i  (One-hall  natural  size,  i 

illustrated  in  figures  5  and  6,  from  photographs  taken  November  22, 
1909,  after  the  leaves  had  fallen.  The  garden-soil  pot  contained  only 
.i  f<  \  stray  roots,  and  the  -lender  stems  were  only  2  inches  high. 
The  pot  containing  blueberry  soil  was  filled  with  a  dense  mass  of 
roots,  and  although  the  plant  had  not  been  repotted  when  it  needed 
repotting,  the  largest  stem  was  nevertheless  11  inches  long  and  the 
weight  of  that  part  of  the  plant  above  ground  was  fifty-one  times 
that  of  the  corresponding  part  of  the  garden-soil  plant. 

(2)    THE  SWAMP  BLUEBERRY    Hers    NOT  THRIVE  IN    \    111   w  II  Y    MANURED  SOIL. 

Iii  May.  1909,  two  healthy  and  vigorous  blueberry  seedlings  were 

sent    for  trial  to  one  of  the  agricultural  experi n1  stations.     They 

were  set  out  in  a  soil  that  was  known  to  be  suitable  for  these  plant-. 
for  old  blueberry  bushes  had  been  growing  there  for  several  years. 
54708       Bull.  193     10 2 


18 


EXPERIMENTS  IN  BLUEBERRY  CULTURE. 


The  man  who  put  the  blueberry  seedlings  in 
the  ground,  however,  misunderstanding  the 
directions  sent  him,  filled  in  the  holes  in  which 
he  set  the  plants  with  alternate  layers  of  soil 
and  well-rotted  stable  manure.  The  writer  ex- 
amined the  plants  on  August  "27.  1909,  when 
they  should  have  been  either  growing  vigor- 
ously or,  with  mature  foliage,  ripening  their 
wood  for  the  winter.  Instead  they  had  lost 
nearly  all  their  older  leaves  (hough  still  main- 
taining a  feeble  and  spindling  growth  at  the 
ends  of  the  larger  stems.  The  adjacent  old 
bushes  growing  in  precisely  the  same  soil,  ex- 
cept that  it  had  not  received  the  heavy  appli- 
cation of  manure,  bore  at  the  same  time  vigor- 
ous dark-green  foliage  and  were  ripening  the 
wood  of  their  stout  twigs  and  laying  down 
their  flowering  buds  for  the  following  year. 
The  manured  plants  when  dug  up  and  exam- 
ined showed  no  new  root  growth  whatever  in 
the  manured  soil  outside  the  old  earth  ball,  and 
most  of  the  roots  on  the  surface  of  the  ball 
itself  were  dead. 

Another  experiment  may  be  cited  to  show 
the  injurious  effect  of  heavy  manuring.  On 
December  22,  1908,  six  blueberry  seedlings  were 
transplanted  into  as  many  glass  pots  in  a  good 
blueberry  soil,  ami  six 
other  seedlings  were 
potted  in  the  same 
manner,  except  that  to 
each  1  wo  parts  of  blue- 
berry soil  one  part  of 
well-rotted  but  un- 
leached  cow  manure 
was  added.  At  first 
the  manured  plants 
appeared,  superficially, 
to  he  doing  better  than 
those  not  manured,  for 
in  the  former  the  pro- 
duction of  new  leaves 
a  n  d  t  h  e  continued 
growth  of  the  stem  tip 
L93 


Pig.  5.     Blueberry  seedling 

in  rich  panlcn  soil,    i  <  >nc 
hiilf  natural  size,  i 


Fig.  6.  Blueberry  seedling 
in  peat  mixture.  (One- 
half  natural  slz6.) 


BLUEBERRIES    WANTING    !  N    LIMESTONE    SOILS.  19 

were  not  interrupted  by  the  potting,  while  in  the  plants  nol  manured 
there  was  a  temporary  1  > 1 1 1  definite  stopping  of  stem  growth  imme- 
diately after  the  potting.  The  apparent  superiority  of  growth  in  the 
manured  plants,  above  ground,  continued  for  about  three  weeks.  Be- 
liiw  ground,  the  roots  of  the  two  cultures  showed  directly  opposite 
results.  In  the  plants  without  manure,  new  root  growth  began  a  few 
days  after  potting.  At  the  end  of  three  week-  the  development  of  an 
extensive  tern  was  well  under  way  and  the  plants  were  nearly 

ready  for  a  period  of  \  igorous  stem  growth.  In  the  manured  plants. 
however,  either  do  root  growth  took  place  or  only  a  slight  amount. 
the  new  rootlets  being  fewer,  shorter,  and  stouter  than  in  normal 
plant-.  The  old  rootlets  tinned  brown  and  appeared  to  be  dead  or 
dying.  (See  p.  64.)  At  the  end  of  live  week-  the  growth  of  the 
tops  was  N'-ry  slow.  About  ten  day-  later,  on  February  6,  a  bright 
warm  day,  the  lower  leaves  on  three  plants  withered,  and  within  a 
few    week-  all  six  of  the  manured  plants  were  dead. 

I  .".  I    Till     SWAMP  BLUEBEBIH    S    KOI    THRIVE  IN     \.  SOIL  MADE  SWEET  B1     LIME. 

Iii  its  natural  distribution  the  blueberry,  like  almosl  all  plants 
of  this  and  the  heather  family,  avoids  limestone  soils.  The  fertile 
limestone  areas  of  western  New  York,  of  Ohio,  of  Kentucky,  and 
of  Tennessee  lack  the  blueberry,  the  huckleberry,  the  laurel  {Kalmia 
Jatifolia),  and  the  trailing  arbutus  (Epigaea  repens).  The  State 
of  Alabama,  as  described  by  Charles  Mohr  in  volume  6  of  Contri- 
butions from  the  United  States  National  Herbarium,  is  traversed 
from  east  to  west  in  the  general  latitude  of  Montgomery  by  a  strip 
of  dark  calcareous  soil,  35  to  r>  miles  in  width,  the  so-called  "black 
belt,"  which  constitutes  the  great  agricultural  region  of  the  State. 
The  noncalcareous  area-  north  and  south  of  this  strip  have  in  their 
i-  a  characteristic  undergrowth  of  blueberries  and  closelj  re- 
lated plant-,  including  huckleberries,  farkleberries,  and  deerberries. 
In  the  intermediate  belt  of  Mack  limestone  soil,  just  described,  the 
plant-  of  blueberry  relationship  are  almost    wholly  wanting. 

In  an  article  entitled  "The  Soil  Preference-  of  Certain  Alpine 
and  Subalpine  Plants,"0  Mr.  M.  L.  Fernald  discusses  the  natural 
distribution  of  over  250  species  of  plants  found  in  the  cold  parts 
of  the  northeastern  United  Mate-  and  Canada.  All  the  blueberries 
umerates,  five  species,  avoided  calcareous  -oil-,  ami  the  other 
plants  of  the  blueberry  and  heather  families  almost  without  excep- 
tion occurred  likewise  on  noncalcareous  formation-. 

The  writer'-  own  experiments  in  growing  blueberries  in  limed 
-ml-   have   not    proceeded    with    the  same   -inoothne-  of   his 

other  experiments,  but  the  results,  though  at  first  misleading,  have 
uniformly  been   exceedingly   instructive,  though   not   always   in   the 

Rhodora,  vol.  0,   mo?,   pp.   L49  L93. 
193 


20  EXPERIMENTS   IN    BLUEBERRY   CULTURE. 

direction  originally  contemplated,  and  in  the  end  have  been  fully 
conclusive. 

On  May  l;<'>.  1008,  six  blueberry  seedlings  were  potted  in  six  14- 
ounce  drinking  glasses  in  a  good  peaty  blueberry  soil,  in  which, 
however,  1  per  cent  of  air-slaked  lime  "  had  been  mixed  immediately 
before  the  potting  was  done.  Six  other  plants  were  similarly  potted, 
but  without  the  addition  of  lime.  The  unlimed  plants  grew 
normally.  The  younger  leaves  of  the  limed  plants,  however,  began 
to  wilt  the  same  day  on  which  they  were  potted.  On  June  1  all 
the  leaves  on  all  six  plants  were  withered,  though  parts  of  the  steins 
were  still  green  and  plump.  The  leaves  did  not  turn  purplish  or 
yellowish,  as  is  usual  with  sickly  blueberry  plants,  but  either  re- 
tained their  green  color  after  withering  or  turned  brown.  No  new 
root  growth  took  place  in  any  of  the  limed  pots,  and  by  July  10  all 
the  plants  were  dead. 

Another  series  of  six  plants,  also  potted  on  May  26,  11)08.  but  m 
a  sterile  soil  containing  no  peat,  by  accident  received  a  very  small 
amount  of  lime.  Most  of  the  leaves  on  these  plants  withered  during 
the  first  few  days,  but  the  plants  subsequently  recovered  and  made 
as  good  growth  as  could  have  been  expected  from  the  general  char- 
acter of  their  soil. 

From  these  experiments  the  writer  concluded  that  the  blueberry 
was  exceedingly  sensitive  to  lime  and  that  the  slightest  admixture 
of  it  in  the  soil  would  be  immediately  fatal  to  the  life  or  at  least 
the  health  of  a  blueberry  plant.  This  conclusion,  however,  was 
erroneous,  as  subsequent  experience  showed.  This  first  experiment 
may  therefore  be  dismissed  with  the  explanation  that  in  all  proba- 
bility the  immediate  collapse  of  the  plants  was  due  to  a  caustic  effect 
of  the  lime  used.  In  none  of  the  later  iime  experiments  did  this 
immediate  collapse  occur  and  in  none  was  the  lime  so  applied  that 
it  came  into  contact  with  the  blueberry  roots  while  in  a  caustic 
condition. 

Still  laboring  under  an  erroneous  conception  of  the  supersensi- 
tiveness  of  the  blueberry  plant  to  minute  quantities  of  lime,  the 
writer,  desiring  to  produce  fresh  examples  of  this  phenomenon,  in 
November,  1008,  placed  a  very  small  quantity,  a  few  milligrams,  of 
air-slaked  lime  on  the  surface  of  the  soil  in  each  of  three  '-'-inch 
pots  containing  a  small  blueberry  plant.  No  effect  was  produced 
either  at  first  or  for  several  weeks.  On  December  19,  L908,  a  large 
surface  application  of  carbonate  of  lime  was  made  to  the  same  three 
plants,  a  gram  to  each  pot.  and  the  lime  was  washed  down  with 
water.  The  expected  collapse  did  not  occur.  The  limed  plants  con- 
tinued to  grow  as  luxuriantly  as  their  unlimed  neighbors.     The  coh- 

0 Computed  en  (lie  dry  weight  of  the  soil. 

i  !>:: 


>l,<>\\     PERI  OLATION M  I.    CHROUGH    PEAT.  21 

elusion  \\  as  reached  that  the  reason  why  the  growth  of  the  plants  had 
not  been  affected  was  because  the  lime  had  nol  penetrated  sufficiently 
ititD  the  soil.  Another  and  more  drastic  experiment  was  therefore 
determined  upon. 

On  March  LO,  L909,  sis  blueberry  plants  in  Pinch  pots  containing 
::  good  blueberry  soil  were  sel  apart  from  their  fellows  and  watered 
with  ordinary  limewater,  a  saturated  solution  of  calcium  oxid,  1.25 
grams  per  liter  of  water.  The  applications  made  were  of  such  an 
amount  that  the  soil  in  the  pot  was  thoroughly  wetted  cadi  time,  and 
usually  a  small  excess  quantity  ran  through  the  hole  in  the  bottom 
of  the  pot. 

For  more  than  seven  months,  until  October  22,  1909,  these  pots 
received  no  other  water  than  limewater.  During  this  period  the 
plants  continued  to  grow  in  a  normal  manner,  their  average  height 
increasing  from  I'  to  II  inches.  The  lime  appeared  to  have  no 
deterrenl  effeel  whatever  on  the  growth  of  the  plant-.  A  computation 
based  on  the  total  amount  of  limewater  used  showed  that  each  pot 
must  have  received  about  18  grams  of  lime.  An  analysis  of  the  -nil 
in  one  of  the  puts  after  the  limewater  applications  had  ceased  gave 
II  grams.  This  amount  was  enormous,  considered  from  the  stand- 
point of  agricultural  usage.  The  soil,  which  had  about  one-third 
the  weight  of  an  ordinary  soil,  was  over  8  per  cent  lime.  This  is  the 
equivalent  of  aboul  25  ton-  of  lime  per  acre  mixed  into  the  upper 
»'.  inches  of  the  -oil. 

Now.it  was  already  known  from  the  experiment  described  on  page 
'_'•">  that  in  this  soil  when  containing  as  much  as  1  per  cent  of  lime 
blueberry  plants  should  either  die  or  barely  remain  alive.  A-  a 
matter  of  fact  these  limewater  plant-  were  making  excellent  growth. 

A    careful   examinati f  the  contents  of  one  of  the   pot-   vva-   then 

made.  The  surface  of  the  -oil  was  covered  with  a  hard  gray  crust 
of  lime.  Immediately  underneath  for  a  depth  of  about  half  an  inch 
the  oil  was  black  and  contained  no  live  blueberry  root-.  There  was 
a  zone  of  the  same  black  rootless  -oil  along  the  wooden  label  that 
reached  from  the  top  to  the  bottom  of  the  pot.  In  all  other  parts 
of  the  dark-brown  peaty  -oil  there  was  a  dense  mas-  of  healthy 
roots,  which  reached  down  also  into  the  open  -pace-  among  the 
broken  rocks  in  the  bottom  of  the  pot.  The  lime  appeared  to  have 
penetrated  only  into  the  superficial  portions  of  the  -oil.     A  chei 

howed  that  the  Mack  rootle--  layer  was  densely  impregnated 
with  lime,  while  the  brown  peatj  portion  containing  the  growing 
root-  -till  gave  the  acid  reaction  thai  vvas  characteristic  of  the  whole 
potful  of  soil  he  I  ore  t  he  limewater  applications  began. 

Since  all  the  water  that  the  limeless  root-bearing  portion  of  the 
soil  had  received  during  the  preceding  seven  month-  had  come  from 
the  limewater  applications,  it   was  evident   that   the  lime  contained 

193 


22  EXPERIMENTS    IN    BLUEBERRY   CULTURE. 

in  the  limewater  had  been  deposited  in  the  upper  layer-  of  the  soil. 
The  following  laboratory  experiment  confirmed  this.  A  small  quan- 
tity of  the  acid  peaty  soil  used  in  growing  blueberries  was  placed 
in  a  glass  vessel  and  moistened.  Then  dilute  limewater  reddened  by 
the  addition  of  phenolphthalein.  a  substance  giving  a  delicate  color 
test  for  alkalies  such  as  lime,  was  stirred  into  the  soil  and  the  mixture 
poured  into  an  ordinary  paper  filter.  The  water  came  through  the 
filter  without  a  trace  of  red  color,  showed  none  after  boiling,  to  drive 
off  any  possible  carbonic  acid,  and  when  tested  with  ammonia  and 
ammonium  oxalate  showed  not  a  trace  of  lime.  The  precipitation 
of  the  lime  had  been  complete  and  practically  instantaneous.  Only 
ten  seconds  had  elapsed  between  the  time  when  the  limewater  was 
added  to  the  soil  and  the  time  when  the  liquid  entirely  free  from  lime 
began  to  drop  through  the  filter. 

In  order  to  ascertain  whether  a  large  part  of  the  lime  in  the  lime- 
water  used  on  the  plants  may  not  have  passed  through  the  pots  by 
running  down  the  partially  open  channel  along  the  label,  some  lime- 
water  was  poured  upon  the  surface  of  one  of  the  pots.  The  excess 
water  that  soon  began  to  drip  through  the  bottom  of  the  pot  was 
tested  for  lime.  It  was  found  that  while  the  limewater  poured  into 
the  pot  contained  0.1014  per  cent  of  lime,  the  water  that  came 
through  contained  only  0.0046  per  cent.  In  other  words  a  pot  of  soil 
that  for  over  seven  months  had  been  used  essentially  as  a  limewater 
filter  still  continued  to  extract  over  95  per  cent  of  the  lime  contained 
in  the  limewater  that  was  passed  through  it.  notwithstanding  the 
fact  that  there  was  a  partially  open  channel  down  one  side  of  the 
pot.  It  is  believed  that  had  the  soil  been  evenly  compacted  in  the 
pot  no  lime  whatever  would  have  been  able  to  pass  through,  hut  that 
all  would  have  been  precipitated  in  the  uppermosl  layers. 

While  the  experiment  ha-  no  important  bearing  on  the  subject  of 
blueberry  culture  it  is  of  very  great  significance  in  its  bearing  on  the 
method  of  applying  lime  to  acid  soils  in  ordinary  agricultural  prac- 
tice. A  surface  application  id'  lime  would  have  no  appreciable  effed 
in  neutralizing  the  acidity  of  a  soil  unless  the  -oil  was  so  sandy  or 
gravelly  or  otherwise  open  that  the  rain  water  containing  the  dis- 
solved lime  could  run  down  through  it  practically  without  obstruc- 
tion. A  surface  dressing  of  lime  would  have  little  effecl  in  neutraliz- 
ing the  acidity  of  an  old  meadow  or  pasture.  To  secure  full  action 
of  the  lime,  as  now  generally  recognized  in  the  best  agricultural 
practice,  requires  its  intimate  mixing  villi  the  -oil.  such  as  can  be 
accomplished  by  thorough  harrowing,  especially  after  putting  the 
lime  beneath  the  surface  with  a  drill.  A  full  discussion  id'  the  phys- 
ical reasons  for  the  deposition  of  the  lime  in  the  upper  layer-  of  the 
-oil.  when  not  worked  into  it  mechanically.  i<  given  in  Bulletin  .V_'  of 
Bureau  of  Soils,  published  in  1  DOS. 


[NJUBI01  S    II  II  I    I     OF    LIME 


Among  the  experiments  with  blueberry  seedlings  in  different  soil 
mixtures  started  on  December  22,  L908,  was  one  in  which  six  plants 
set  in  »lass  pots  in  ;i  peaty  soil  thoroughly  intermixed  with 
1  per  eenl  of  carbonate  of  lime.  The  first  difference  that  showed  be- 
tween these  and  unlimed  plants  in  the  same  soil  was  the  much  feebler 
root  growth  of  the  limed  plants.  This  was  followed  by  an  evident 
tendency  toward  feebler  stem  growth.  The  relative  condition  of  the 
two  cultures  on  April  13,  1909,  is  shown  by  photographs  of  represent 
at  iw  plants  reproduced  as  figures  7  and  8.    The  later  progress  of  this 


Bluebern   s Illns  in  peal  mixture      Fig.  8.      Blm  tiling  In  peal  mixture 

limed.      (One-naif  natural  size.)  unlimed.      (On<  uralsize.) 


experiment  was  interrupted,  however,  and  its  average  results  vitiated 
-c  the  roots  of  -nine  of  the  limed  plants  found  their  way  through 
the  holes  in  the  bottom  of  the  pot-  and  obtained  nourishment  from 
the  unlimed  material  in  which  the  pots  were  plunged.  Such  plants 
made  nearly  as  good  growth  as  the  unlimed  plants.  On  November 
27,  1909,  there  remained  only  one  of  the  limed  plants  whose  root? 
were  all  inside  the  pot.  This  plant  was  feeble  and  small,  its  stem 
being  only  •_'!  inches  high,  lis  inferiority  to  the  unlimed  plant-  was 
almost  as  conspicuous  as  that  of  the  garden-soil  plant-  described  on 
17  and   illustrated   in   figure  5. 


24  EXPERIMENTS  IN  BLUEBERRY  CULTURE. 

(4)  The  swamp  blueberry  does  not  thrive  in  a  heavy  clay  soil. 

In  its  natural  geographic  distribution  the  blueberry  shows  an 
aversion  to  clay  soils.  Its  favorite  situations  are  swamps,  sandy 
lands,  or  porous,  often  gravelly  loams.  When  a  blueberry  plant 
grows  upon  a  clay  soil  it  is  usually  found  that  its  finer  feeding  roots 
rest  in  a  layer  of  half-rotted  vegetable  matter  overlying  the  clay. 
Often  in  such  situations  the  dense  covering  of  interwoven  rootlets 
and  dark  peatlike  soil  may  be  ripped  from  the  surface  in  a  layer 
little  thicker  than  a  door  mat  and  of  much  the  same  texture.  The 
roots  of  the  blueberry  do  not  penetrate  freely  into  the  underlying  clay. 

In  greenhouse  cultures  the  blueberry  shows  the  same  aversion  to 
clay  soils.  Various  series  of  blueberry  seedlings  were  potted  on  May 
26,  L908,  in  different  soils  in  ordinary  large  drinking  glasses.  For 
one  set  of  six  plants  a  stiff  clayey  soil  was  used,  such  as  is  common 
in  the  neighborhood  of  Washington,  D.  C.  The  soil  in  the  glass  was 
mulched  to  the  depth  of  nearly  an  inch  with  half-rotted  leaves.  In 
another  six  glasses  were  set  six  similar  plants  in  a  peat  soil,  the  sur- 
face mulched  in  the  same  way  as  the  others. 

In  other  experiments  with  this  clay  soil  in  earthen  pots,  the  growth 
of  the  plants  had  always  been  poor.  The  present  experiment  was  no 
exception.  But  the  feature  of  greatest  interest  was  the  behavior  of 
the  roots.  Plate  I,  from  photographs  taken  October  5,  1908.  shows 
the  root  systems  of  typical  plants  in  the  two  soils.  In  the  clay  soil 
almost  no  root  development  took  place,  and  in  the  illustration  no 
routs  are  visible.  The  interrupted  black  lines  in  the  clay  are  tunnels 
made  by  larva;  or  other  animals.  In  the  moist  leaf  mulch  covering 
the  clay,  however,  the  plant  developed  its  roots  extensively.  Some  of 
the  plants,  probably  because  they  were  set  too  deeply  in  the  clay 
when  the  potting  was  done,  failed  to  send  their  roots  up  into  the 
mulch,  and  such  plants  were  much  inferior  in  their  growth  to  those 
that  found  the  rotted  leaves.  In  the  other  gins-  i-  shown  the  normal 
root  growth  of  a  blueberry  in  a  soil  suited  to  it. 

(5)  The  swamp  blueberry  does  not  thrive  in  a  thoroughly  decomposi  d  leaf 

mold,  such  as  has  a  neutral  reaction. 

It  had  been  found  in  earlier  experiments  that  certain  -oil-  com- 
posed in  part  of  imperfectly  rotted  oak  leaves  were  good  for  growing 
blueberries.  On  the  supposition  that  the  more  thoroughly  rotted  this 
material  was  the  better  suited  it  would  be  for  blueberry  growing,  a 
quantity  of  old  leaf  mold  was  secured  for  an  experiment.  The  mold 
was  black-,  mellow,  and  of  fine  texture.  The  mixed  oak  and  maple 
leaves  from  which  it  was  derived  had  been  rotting  for  about  five 
years,  until  all  evidences  of  leaf  structure1  had  disappeared.  It  had 
the  same  appearance  a-  the  black  vegetable  mold  thai  form-  in  rich 
woods  where  trilliums.  spring  beauty,  and  bloodroot  delight  to  grow. 

193 


Bui.  193,  Bureau  of  Plant  Indjstty.  U.  S.  Dep: 


Plate  I. 


£ 

■ 

1        1 

i m 

IN. i  [JRIOUS    Mil.'    I    OF    l.l   \l     MOLD.  25 

On  February  20,  L909,  25  blueberry  seedlings  were  potted  in  ".-inch 
earthenware  pots  in  a  mixture  consisting  of  eight  part-  by  bulk  oi 
the  leaf  mold  just  described,  one  part  of  clean  sand,  and  one  pari  of 
clayej  loam  derived  from  rotted  grass  turf.  Fifty  other  plant-  were 
potted  in  the  same  manner  except  that  in  place  of  the  mold  a  peat 
was  used  known  from  earlier  experiments  to  be  well  suited  to  blui 
berrj  growing.  The  plant-  were  kept  in  the  greenhouse  until  warm 
weather  when  they  were  placed  outdoor-.  All  were  given  the  same 
treatment,  a  treatmenl  favorable  to  good  growth. 

It  had  been  expected  that  the  plant-  in  the  leaf  mold  would  -how  a 
vigorous  growth,  and  it  was  hoped  that  the  mold  might  prove  even 
superior  to  the  peat  for  blueberry  soil  mixture-.  The  experiment  as 
ii  progressed,  however,  showed  that  such  was  not  the  case.  The  leal* 
mold  proved  to  be  not  merely  not  a  good  soil  for  blueberries  but  an 
extremely  pom-  one,  as  the  following  particular-  will  -how. 

When  the  plants  were  potted  they  averaged  about  •_'!  inches  in 
height.  On  May  29  the  peat-soil  plant-  had  an  average  heighl  of  ~\ 
inches,  while  the  leaf-mold  plant-  averaged  1]  inches.  At  this  time 
the  herbage  of  the  leaf-mold  plant-  was  decidedly  purpled  and  yel- 
lowish, a  coloration  which  they  had  taken  on  SOOn  after  they  were 
polled  and  from  which  they  never  fully  recovered.  At  the  end  of  the 
season,  after  the  leaves  were  shed,  the  peat-soil  plants  averaged  \'-\\ 
inches  in  height  and  the  lea  f-mold  plant-  7  |  inches.  <  )n  November  29, 
1909,  five  average  plant-  from  each  lot  were  cut  oil'  at  the  surface  of 
the  ground  and  weighed.  The  weight  of  the  stems  from  the  lea  f-mold 
plant-  was  less  than  one-fifth  that  from  the  plants  in  the  good  blue- 
berry -oil. 

When  these  plant-  were  removed  from  their  original  seed  bed  to 
he  transplanted  to  the  3-inch  pots,  such  of  the  original  -oil  as  clung 
i"  their  i""'  was  not  shaken  off.  It  ;-  believed  that  the  leaf-mold 
plant-  U->\  in  part  on  this  original  -oil  in  making  their  new  growth, 
and  that  without  it  they  would  have  shown  -till  less  increase  in 
height  than  tiny  did.  The  peat-soil  plant-,  moreover,  were  badly  in 
need  of  repotting,  even  in  early  summer,  and  had  they  been  placed  in 
larger  pots  the  difference  in  the  growth  of  the  plant-  in  the  two  soils 
would  have  been  much  greater  than  it  was. 

That  the  influence  of  the  leaf  mold  wa-  directly  deleterious  and 

thai  the  i r  growth  of  the  blueberry  plants  in  it  wa-  not  due  t < .  the 

lack  of  some  element  that  might  have  Keen  furnished  by  the  addition 
■  I  a  -mall  amount  of  the  good  blueberry  -oil  i-  shown  by  certain  inter 
mediate  experiment-.  A.long  with  the  culture-  described  above  were 
carried  two  other-  in  which  the  -oil  mixture-  contained  both  peat  and 
leaf  mold.  In  the  first,  in  which  the  proportion  wa-  peat  '>.  mold  3. 
-and   1.  and  loam   1.  the  average  height   of  the  plants  on  May  29 


26  EXPERIMENTS   IN    BLUEBERRY    CULTURE. 

was  6  inches,  and  at  the  end  of  the  season  124  inches.  In  the  second 
lot,  in  which  the  proportion  was  peat  3,  mold  5,  -and  1.  and  loam  1, 
the  average  height  on  May  29  was  44  inches,  and  at  the  end  of  the 
season  llf  inches.  It  will  be  observed  that  these  two  lots  of  plants 
are  intermediate  in  their  growth  between  the  first  two  and  that  in  all 
four  lots  the  poverty  of  growth  is  roughly  proportional  to  the  amount 
of  leaf  mold  used  in  the  soil. 

That  the  weak  growth  of  the  plants  in  leaf  mold  was  not  caused  by 
a  compacting  of  the  soil  and  a  lack  of  aeration,  due  to  too  small  a 
proportion  of  sand  in  the  mixture,  is  shown  by  still  another  lot  of  25 
plants  which  were  potted  in  a  soil  mixture  having  the  proportion  of 
mold  6,  sand  3.  and  loam  1.  These  plants  averaged  only  4  inches  in 
height  on  May  29  and  6^  inches  at  the  end  of  the  season.  They  grew 
even  less,  therefore,  than  the  plants  with  only  1  part  of  sand  and  8 
parts  of  mold. 

In  Plate  II,  from  a  photograph  made  in  the  winter  of  1909-10,  is 
shown  a  flat  divided  into  three  parts  and  set  on  February  10,  1909, 
with  blueberry  seedlings  of  uniform  size.  The  soil  in  the  middle 
compartment  is  a  mixture  of  leaf  mold  8  parts,  sand  1  part,  and  loam 
1  part.  Iii  the  compartment  to  the  left  the  soil  is  in  the  proportion 
of  kalmia  peat  8.  sand  1.  and  loam  1;  and  in  the  right diand  com- 
partment, kalniia  peat  4,  leaf  mold  4,  sand  1,  and  loam  1.  It  will  be 
observed  that  the  greater  the  amount  of  leaf  mold  the  poorer  the 
growth  of  the  blueberry  plants. 

The  reason  for  the  unexpected  deleterious  effect  of  leaf  mold,  as 
shown  by  these  experiments,  is  given  on  page  29  and  further  discussed 
on  page  35. 

(6)  The   swamp  blueberry  does   not  thrive  in   soils   haying   a  neutral   on 

ALKALINE    REACTION,    BUT   FOR    VIGOROUS    GROWTH    IT   REQUIRES    AN    ACID   SOIL. 

The  consideration  of  this  statement  requires  first  an  understanding 
of  the  means  used  to  determine  whether  a  soil  is  acid  or  alkaline. 
The  simplest  means  is  the  litmus  test. 

While  one  may  become  sufficiently  expert  in  the  use  of  the  litmus 
test  to  form  a  fair  judgment  of  the  degree  of  alkalinity  or  acidity  in 
a  soil,  an  exact  determination  requires  some  different  method,  li 
was  found  that  for  the  weak  acids  prevalent  in  the  peat  soils  to  the 
examination  of  which  the  present  experiments  led.  the  phenol- 
phthalein  test  was  the  most  satisfactory.  II'  a  few  drop--  oi  phe- 
nolphthalein  indicator  be  added  to  a  solution,  the  solution,  if 
alkaline,  turns  instantly  pink,  and  if  acid  or  neutral  its  color  does 
not  change.  The  application  of  this  phenomenon  to  the  determina- 
tion of  the  degree  of  acidity  of  an  acid  solution  i-  as  follows:  A 
definite  amount  of  the  solution,  usually  100  cubic  centimeters,  is 
placed  in  a  beaker,  a  few  drops  of  an  alcoholic  solution  of  phenol- 
193 


Bui.  193,  Bu'  ry,  U.  S.  Dept.  of  Agriculture. 


Plate  II 


HOD  OF   Ti  -  OIL    v  inn  i  .  27 

phthalein  are  added,  and  into  this  is  stirred  drop  by  drop  from  m 
graduated  glass  tube  provided  with  a  stopcock,  known  as  a  burette, 
a  measured  amount  of  some  alkaline  solution  of  known  strength, 
commonly  a  one  twentieth  normal  solution,  as  ii  is  known  to  chem- 
ists, of  sodium  hydrate.  When  a  sufficient  amount  of  the  sodium- 
hydrate  solution  has  been  dropped  into  the  beaker,  the  acidity  of  the 
acid  solution  becomes  neutralized  and  ii  turns  pink.  A  reading  is 
made  on  the  burette  showing  the  exact  amounl  of  the  sodium-hydrate 
solution  used  in  effecting  the  neutralization.  From  this  reading  is 
computed  the  degree  of  acidity  expressed  in  fractions  of  a  normal 
acid  solution.  Now  LOO  c.  c.  of  a  normal  acid  solution  would  require 
for  it-  neutralizat  ion  LOO  c.  c.  of  a  normal  solution  of  sodium  hydrate, 
or  2,000  c.  c.  of  a  one-twentieth  or  0.05  normal  solution.  In  a  test  of 
one  of  the  acid  nutrient  solutions  used  in  the  blueberry  cultures, 
L8  c.  c.  of  :i  0.05  normal  solution  was  required  to  neutralize  the  acidity 
of  LOO  c.  c.  of  the  acid  solution.  Since  L8  c.  c.  of  a  0.05  normal 
.solution  is  the  equivalent  of  one-twentieth  that  amount,  or  0.9  c.  c.  of 
a  normal  solution,  the  degree  of  acidity  of  this  acid  solution  is  0.009 
normal.  It  requires  an  equal  amount  of  a  0.009  normal  alkaline 
solution  to  neutralize  it. 

In  applying  this  phenolphthalein  test  to  soils  the  same  scale  is 
used.  A  soil  i-  regarded  as  having  normal  acidity  when  the  acid  ex- 
isting in  a  gram  of  the  soil  if  dissolved  in  1  c.  c.  of  water  gives  a  nor- 
mal acid  solution.  If  a  soil  were  described  as  having  an  aciditj  of 
0.02  normal,  it  would  mean  that  the  extract  of  LOO  grams  of  it  in  100 
c.  c.  of  water  would  be  a  0.02  normal  acid  solution;  that  is.  that  LOO 
C  c.  of  the  solution  would  contain  -1  c.  c.  of  a  normal  acid  solution. 

'The  method  of  extraction  followed  for  all  the  soil  acidity  tests 
given  in  this  paper  is  a-  follow-:  The  -oil  is  first  air  dried  at  an  ordi- 
nary room  temperature.  Ten  grams  are  then  weighed  out.  shaken  thor- 
oughly with  2 <■.  of  hot   water,  and  allowed  to  stand  oxer  night. 

In  the  morning  too  c.  c.  is  filtered  oil'  and  boiled  to  drive  away  any 

carbon  dioxid  present.     The  solution  i-  then  titrated  with  a  0.05  

mill  solution  of  sodium  hydrate,  using  phenolphthalein  a-  an  indi- 
cator. All  the  tests  were  made  by  Mr.  .1.  I-'.  Breazeale.  of  the  Bureau 
of  Chemistry,  to  whom  the  writer  i-  greatly  indebted  for  many  cour- 
tesies and  suggestions  on  the  chemical  side  of  the  experiment-. 

The  expression  •■normal  solution "  used  in  this  paper,  it  must  be 
understood,  i-  the  normal  solution  of  chemists,  not  of  surg 
Surgeons  use  the  expression  "  normal  -alt  solution  '"  to  describe  a  cer- 
tain weak  solution'of  common  salt  in  water  which  has  the  same 
osmotic  pre— ure  a-  the  blood.  A  normal  solution  in  chemistry  is  a 
solution  of  certain  fixed  strength,  or  concentration,  based  on  the 
molecular  weight  of  the  substance  under  considerat  ion.     Normal  solu- 

193 


28  EXPERIMENTS  IN  BLUEBERRY  CULTURE. 

tions  of  the  various  acids  have  the  same  degree  of  acidity.  Normal 
solutions  of  alkaline  substances  are  equal  to  each  other  in  alkalinity. 
A  measured  amount  of  a  normal  solution  of  an  acid  will  exactly 
neutralize  an  equal  amount  of  a  normal  solution  of  an  alkaline  sub- 
stance. 

In  considering  the  degree  of  acidity  from  the  standpoint  of  the 
sense  of  taste  it  is  convenient  to  remember  that  the  juice  of  an  ordi- 
nary lemon  is  very  nearly  a  normal  solution  of  citric  acid.  The  juice 
of  the  lemon  contains  usually  from  6  to  7  per  cent  of  citric  acid.  A 
normal  solution  of  citric  acid  is  6.4  per  cent.  When  the  juice  of  a 
lemon  is  diluted  to  about  ten  times  its  original  bulk,  as  in  a  large 
drinking  glass,  one  has  approximately  a  0.1  normal  acid  solution. 
When  diluted  to  100  times,  making  about  a  0.01  normal  solution, 
there  remains  only  a  faint  taste  of  acidity.  The  acidity  of  water 
after  standing  long  in  contact  with  peat  in  a  barrel  sometimes  reached 
0.005  normal.  Bog  water,  or  peat  water,  is  sometimes  appreciably 
acid  to  the  taste. 

Returning  now  to  a  consideration  of  the  statement  that  the  swamp 
blueberry  does  not  thrive  in  a  neutral  or  alkaline  soil  an  experiment 
in  this  direction  may  first  be  cited,  The  experiment  was  made  with 
twelve  small  glass  pots,  each  containing  a  blueberry  seedling.  The 
soil  in  the  pots  was  a  clean  river  sand.  The  plants  had  been  in  these 
pots  for  eight  weeks,  watered  with  tap  water.  The  amount  of 
nourishment  they  had  received  during  this  time  was  therefore  very 
small,  especially  since,  when  transplanted  into  the  pots,  all  the  soil 
of  the  original  seed  bed  had  been  carefully  removed  from  the  roots. 
Nevertheless  during  these  eight  weeks  all  the  plants  had  made  exten- 
sive, even  luxuriant,  root  growth.  The  tops,  however,  had  made  no 
growth.  There  had  been  complete  stagnation  or  withering  of  the 
youngest  leaf  rudiments,  and  the  mature  leaves  became  and  remained 
deeply  purpled. 

Beginning  on  February  IT,  1909,  eight  weeks  after  the  plants  had 
been  potted  in  the  sand,  as  already  stated,  Ww  of  the  pots  were  wa- 
tered with  an  acid  nutrient  solution  made  up.  in  accordance  with  the 
advice  of  Mi-.  Karl  F.  Kellerman,  of  the  Bureau  of  Plant  Industry,  as 
follows: 

Potassium  nitrate  (KX<>::) 1.  Ogram. 

Magnesium  sulphate  (MgS04) 0.4 gram. 

Calcium  sulphate  M';iS<>,t 0.5 gram. 

Calcium  monophosphate  (CaHiPsO  |  0.5 gram. 

Sodium  chlorid   (NaCl) 0.5gram. 

Ferric  chlorid  (FeCU) Trace. 

Water 1,  000  c.  c. 

This  solution  gave  an  acidity  test  of  0.012  normal. 

193 


[NJURIOUS    MM'    1    OF  ALKALINE  SOILS.  29 

Five  other  plants  from  the  same  twelve  were  watered  with  an  alka 
line  nutritive  solution  of  the  following  composition : 

Potassium  nitrate  (KNOa) 1.0  gram. 

Magnesium  sulphate  (MgSO  i  0,  Lgram. 

Calcium  sulphate  (CaSO<)  O.Sgram. 

Potassium  diphosphate   (KH»PO*)  0.4gram. 

Sodium  chlorid   (NaCl) 0.5  gram. 

Ferric  chlorid  i  FeCla)  Trace. 

Water     l.OOOc.e. 

By  the  addition  of  a  sufficient  quantity  of  sodium  hydrate  the  re- 
action  of  tlii-  solution    was   made  alkaline  to  the  degr< f  0.006 

normal. 

Two  of  the  twelve  plants  were  left  as  checks,  being  still  watered 
w  ith   tap   water. 

On  March  l'.~>.  thirty-six  days  after  the  watering  began,  the  five 
plants  fed  with  the  acid  nutritive  solution  were  restored  to  a  nearlj 
normal  green  color,  and  all  had  begun  to  put  out  healthy  new  growth. 
The  two  check  plants  watered  with  tap  water  were  -till  red-purple 
and  stagnant.  Of  the  five  plants  watered  with  the  alkaline  nutrient 
solution,  three  were  stagnant  and  somewhal  purplish,  one  was  dying, 
and  one  w  a-  dead. 

Figures  9  and  10,  from  photographs  taken  on  April  L5,  1909, 
-how  ;i  typical  stagnant  plant  that  had  been  watered  with  the  alka- 
line solution,  ami  a  typical  plant  watered  with  the  acid  solution  which 
had  begun  to  make  new  growth  from  the  summit  of  the  old  -tern  and 
was  pushing  out  a  vigorous  new  shoot  from  the  base.  The  experi- 
ment was  terminated  not  long  afterwards,  but  there  was  every  pros- 
pect that  had  it  been  continued  the  acid  fed  plant-  would  soon  have 
made  grov  th  comparable  with  that  shown  in  figure  8  (p.  23). 

Looking  toward  the  acidity  or  alkalinity  of  the  other  culture-  thus 
far  cited,  it  maj  be  stated  that  the  rich  garden  soil  described  on 
pag  1  I.  which  was  so  remarkably  deleterious  to  blueberry  seedlings, 
was  alkaline.  The  r —  cuttings  and  the  alfalfa,  which  grew  so  well 
in  that  mixture,  much  prefer  a  somewhat  alkaline  soil.  Indeed, 
alfalfa  can  not  be  grown  with  any  degree  of  success  in  any  soil 
except  one  with  an  alkaline  reaction.  When  grown  in  the  humid 
eastern  United  States  alfal  fa  is  rarely  successful,  except  on  calcareous 
soil-,  unless  the  natural  acidity  of  the  soil  has  Keen  neutralized  by 
suitable  applical  ions  of  lime. 

I  ■  limed  soil,  deleterious  to  blueberry  plant-,  described  on  page 
23,  gave  a   neutral   reaction  with   phenolphthalein. 

The  heavy  clay  soil  described  on  pap'  24,  in  which  blueberry  plants 
made  very  little  growth,  was  neutral. 

The  thoroughly  decomposed  leaf  mold  described  on  pages  •_'!  to  26, 
winch  was  shown  by  experiment  to  be  markedly   deleterious  to  the 

103 


30 


EXPERIMENTS    IX     IJLU 1.111. UKY    (  I'L  I  UP.E. 


blueberry,  was  distinctly  alkaline  A  chemical  analysis  of  this  mold 
showed  thai  it  contained  2.86  per  cent  of  calcium  oxid. 

The  good  blueberry  soils  in  all  the  experiments  were  acid,  the  acidity 
at  times  of  active  growth  varying  from  0.025  norma!  down  to  O.OO.j 
normal. 

It  is  of  interest  and  suggestive  of  utility  in  indicating  the  acid  or 
nonacid  character  of  soils  to  record  that  in  the  case  of  the  alkaline 
leaf  mold  described  on  page  24  the  surface  of  the  soil  in  all  the  pots 
became  covered  in  a  few  months  with  a  growth  of  a  small  moss  iden- 


tified through  the  courtesy  of  Mrs.  N.  L. 


Britton  as  Physcomitrium 
/in  an  rsum.  On  the  sur- 
face of  acid  kalmia-peat 
-nil-  the  characteristic 
green  growth  consisted  of 
microscopic  alga1,  accom- 
panied often  by  fern  pro- 
thallia  and  other  mosses, 
but  never  Physcomi- 
trium. 

The  natural  distribu- 
tion of  blueberries  and 
their  relatives  indicates 
their  close  adherence  to 
acid  soils.  They  occur  in 
abundance  throughout  the 
sandy  (  !oastal  Plain  of  the 
Atlantic  seaboard.  They 
occui'  generally  through 
the  cool  humid  hill  lands 
of  New  England.  They 
occur  in  sandy  pine  bar- 
rens a  ad  ]>  e  a  t  bogs 
throughout  the  eastern 
United  States.  They  are  absent,  on  the  contrary,  from  limestone 
soils,  rich  bottom  lands,  and  rich  woods,  where  the  soils  are  neutral 
or  alkaline.  In  the  lower  elevations  of  the  whole  subarid  West,  where 
acid  soils  are  almost  unknown,  these  plants  do  not  occur.  Within 
reach  of  the  fogs  and  heavy  rainfall  of  the  Pacific  coast  or  on  the 
higher  mountains  of  the  interior,  where  conditions  favor  the  devel- 
opment of  acid  soils,  blueberries  occur  again  in  characteristic  abun- 
dance. 

From  an  examination  of  the  report-  of  those  who  have  attempted 

ai   the  agricultural  experiment  stations  to  domesticate  ami  improve 

i  lie  blueberry,  it  is  evident   in  the  light  of  the  present  experiments 

that  the  primary  reason  for  these  failure-  was  that  they  did  not  recog- 

L93 


Fig.  :>. 


Blueberry  s lling  fed  with  alkaline  autrienl 

solution,      i  Natural  size. ) 


i;l  N  EFICIAL    EFFEI    I     OF    PEAT. 


nize  soil  acidity  as  a  fundamental  requirement  of  these  plant?.  Ii 
was  perhaps  natural  to  give  the  blueberry  the  -nine  garden  cultun 
thai  when  applied  to  other  bush  fruits  has  resulted  in  their  distincl 
improvement.  Bui  the  ordinary  garden  operations  tend  to  make  even 
an  acid  soil  neutral  or  alkaline,  and  in  such  a  soil  the  blueberry  does 
not  thrive. 

The  death  and  decay  of  blueberry  roots,  with  which  the  injurious 
effect  of  alkaline  soils  is  associated,  are  discussed  on  pages  64  an 

(7)     Tin     FAVORITE  TYPE  OF  ACID  SOU     FOB     rH       SWAMP  BLUEBEKm     IS  PEAT. 

Although  the  swamp  blueberry  sometimes  grows  on  upland  -oil- 
it-  typical  habitat,  as  its  name  implies,  is  in  swamps  or  bogs.  The 
cranberry,  it  is  well 
known,  is  cultivated  al- 
most exclusively  in  bogs. 
In  clearing  bog  land  pre- 
paratory to  the  planting 
of  cranberries  one  of  1  he 
necessary  precautions  is  to 
remove  all  roots  of  the 
swamp  blueberry.  I  f  the 
roots  are  allowed  to  re- 
main in  the  ground,  they 
send  up  vigorous  shoots, 
and  these,  unless  pulled, 
de\ elop  into  robust  plants 
v\  hich  occupy  the  ground 
to  the  great  injury  of 
the  cranberries.  Large, 
healthy,  and  productive 
bushes  of  the  swamp  blue- 
berry are  frequent,  almost 
characterisl  ic,  inhabitants 
of  the  uncultivated  bor- 
ders of  cranberry  bogs. 

Peat  bogs,  in  the  con- 
ception of  geologists,  are 
incipient  coal  beds.  The 
transformation  of  peat 
into  coal  occupies  verj 
long  perioi  Is,  perhaps  some 
millions  of  years.  Teat  is  made  up  chiefly  of  vegetable  matter. 
the  dead  leaves,  stems,  and  root-,  of  bog  plants  which  are  only 
partly  decayed.  Their  full  decay  IS  prevented  primarily  by 
the    presence  of   water,   which   keep-   away   the   air.      The   bacteria. 


Fig.    II        B  I   with  :\c-iil   mil  li.iii 

solul  Ion.      i  Sal  ural  size,  i 


32  EXPERIMENTS   IN    BLUEBERRY   CULTURE. 

fungi,  and  other  organisms  by  which  ordinary  decomposition  pro- 
gresses can  not  live  under  this  condition  and  decay  is  suspended. 
The  acids  developed  by  this  vegetable  matter  in  the  early  stage-  of 
its  decomposition  are  also  destructive  to  some  of  the  organisms  of 
decay,  especially  bacteria.  These  acids  act  therefore  as  preserva- 
tives and  greatly  assist  in  preventing  decomposition.  So  effective 
are  these  conditions  of  acidity  and  lack  of  oxygen,  assisted  in  north- 
ern latitudes  by  low  temperature,  which  is  also  inimical  to  the  organ- 
isms of  decay,  that  bogs  sometimes  preserve  for  thousands  of  years 
the  most  delicate  structures  of  ferns  and  mosses. 

Tests  have  been  made  of  the  acidity  of  typical  peat  bogs  in  New 
England  where  swamp  blueberries  are  growing.  These  peats  were 
always  found  to  lie  acid  and  the  degree  of  acidity  was  within  the 
range  found  satisfactory  for  blueberry  plants  in  pot  cultures. 

The  reason  why  peat  is  a  particularly  satisfactory  t)Tpe  of  acid  soil 
for  blueberries  is,  apparently,  because  the  acidity  of  peat  is  of  a  mild 
type,  yet  continually  maintained. 

Xot  all  peats  are  acid.  About  the  larger  alkaline  (but  not  destruc- 
tively alkaline)  springs  of  our  southwestern  desert  region  are 
deep  deposits  of  rather  well-decayed  vegetable  matter  that  must 
be  classed  as  peat.  The  characteristic  vegetation  growing  on  these 
peats  is  tide  (Scirpus  occidentalis  and  S.  olneyi).  The  water  of 
one  of  the  great  tide  swamps  of  the  West  (Lower  Klamath  Lake  in 
southern  Oregon),  which  contains  thick  beds  of  peat  formed  chief!) 
from  Scirpits  occidentalis,  has  been  examined  recently  by  Mr.  J.  F. 
Breazeale,  at  the  request  of  Air.  C.  S.  Scofield.  It  was  found  to  con- 
tain sodium  carbonate,  and  the  peat  gave  a  distinctly  alkaline  reaction. 

The  peat  formed  about  marl  ponds  in  the  eastern  United  State- 
is  also,  in  all  probability,  alkaline  unless  formed  at  a  sufficient  dis- 
tance from  the  lime-laden  water  to  be  beyond  the  reach  of  its  acid- 
neutralizing  influence. 

Such  alkaline  peats,  while  not  actually  tried,  are  believed  from 
other  experiments  to  be  quite  useless  for  growing  blueberries.  Cer- 
tain it  is  that  neither  blueberries  nor  any  of  their  immediate  relatives 
are  found  on  these  soils  in  a  wild  state.  In  the  eastern  United 
State-,  however,  such  alkaline  peats  are  comparatively  rare,  and  the 
use  of  the  word  "  peat  "  conveys  ordinarily  the  idea  of  acidity.  All 
the  soils  used  by  gardeners  under  the  name  of  peat  are  acid. 

(S)     I'lVI    SUITABLl     FORTH]     SWAMP  BLUEBERRY    MAT  B]     FOUND  EITHER  IN  BOGS  OR 
ON    Till     SURFACE  OF    Till    GROl   Mi   l  \    SANDY   OAK   OR  PINE  WOODS. 

In  the  vicinity  of  Washington  deposits  of  bog  peat  are  few  and  of 
limited  extent,  and  the  peat  is  thin.  As  a  matter  of  fact  no  bog  peat 
of  local  origin  is  used  by  the  gardeners  and  florists  of  Washington. 
For  growing  orchids,  ferns,  azaleas,  and  other  peat-loving  plants. 
either  peat  shipped  from  New  Jersey  is  used  or  a  local  product  some- 

193 


I  i  IRM  \  I  [ON    OF    KAI..MIA    PEA  I  .  33 

times  known  as  "  Maryland  peat."  This  material  is  not  a  bog  peal  a< 
all,  and  since  it  isof  very  great  interest  in  connection  with  these  blue- 
berry experiments,  for  it  was  the  principal  ingredient  in  a  majority 
of  ilic  successful  soil  mixtures  used,  it  is  desirable  that  the  reader 
have  m  comprehensive  idea  of  its  character. 

Maryland  peat,  as  brought  to  the  greenhouses  of  the  United  States 
Department  of  Agriculture,  consists  of  dark-brown  tin- I's  <>r  mats,  2  to 
I  inches  thick,  made  up  of  partially  decomposed  leaves  interlaced  with 
fine  roots.  It  is  found  in  thicket-  of  the  American  laurel  {Kalmia 
latifolia)  where  the  leaves  of  this  shrub,  usually  mixed  with  those  of 
various  species  of  oak,  have  lodged  year  after  year  and  the  ac- 
cumulated   layer-  have  become  partly  decayed. 

The  nature  of  the  deposit  may  be  easily  comprehended  by  means 
of  the  accompanying  illustrations.  The  photographs  from  which  the 
illustration-  were  made  were  secured  through  the  courtesy  and  skill 
of  Mr.  (i.  X.  Collins,  of  the  Bureau  of  Plant  [ndustry.  The  photo- 
graphs were  made  in  the  month  of  April.  1908,  in  a  laurel  thicket  at 
Lanham,  Md.  Alter  one  photograph  was  made,  the  layer  of  leaves 
represented  by  it  was  removed  and  another  photograph  was  taken 
showing  the  layer  immediately  underneath. 

hi  I  Mate  III.  figure  1.  is  shown  the  top  layer  of  the  lea  I'  deposit  as 
it  appeared  in  April,  L908,  consisting  of  oak  leaves  of  various  species 
which  fell  to  the  ground  in  the  autumn  of  1907.  The  next  under- 
lying layer  is  shown  in  Plate  III.  figure  2.  The  laurel  leave-  here 
shown  are  those  that  fell  in  the  summer  of  L907.  Laurel  being  an 
evergreen,  it-  leaves  arc  not  shed  in  the  autumn  like  those  of  the  oaks. 
They  remain  <>n  the  hush  until  the  new  leaves  of  the  following  spring 
are  fully  developed  and  then  the  old  leave-  begin  t<>  fall.  It  is  this 
circumstance  of  the  fall  of  the  oak  and  laurel  leaves  at  different 
periods  of  the  year  that  enables  one  to  recognize  the  differenl  layers 
and  know  their  exact  age.  The  third  layer,  shown  in  Plate  1  V.  figure 
1.  consists  of  oak  leave-  of  the  autumn  of  1906.  This  layer  was  moist 
and  decomposition  was  well  started.  The  presence  of  fungous  growth 
i-  evident,  a-  i-  also  the  excrement  of  various  -mall  animal-.  Myria- 
pods,  or  thousand-legged  worm-,  and  the  larva'  of  insects  must  play  a 
very  important  part  under  some  conditions  in  hastening  the  de- 
composition of  leaves.  The  fourth  layer.  Plate  [V,  figure  2,  consist- 
ing of  laurel  leaves  shed  in  the  summer  of  L906,  is  in  aboul  the  same 
condition  a-  the  preceding  layer.  In  the  fifth  layer.  Plate  Y.  figure  1, 
are  shown  the  leaves  of  L905,  hut  the  layer  of  oak  leaves  is  not  readily 
separable  from  the  laurel.  The  rotted  leaves  crumble  readily  and 
decomposition  has  so  far  progressed  that  a  few  oak  rootlet-  arc  found 
spread  out  between  the  Rattened  leave-.  Plate  Y.  figure  •_'.  -how-  the 
rotted  lea  f  layer-  of  1904  interlaced  with  the  rootlets  of  laurel  and  oak. 
It  i-  this  root  bearing  layer.  2  inches  or  more  in  thickness,  of  which 
54708°-  Bull.  L93     L0 3 


34  EXPERIMENTS    IX    BLUEBERRY   CULTURE. 

Maryland  peat  is  composed.  The  lower  portions  of  it  reach  a  some- 
what greater  degree  of  decomposition  than  is  here  shown. 

In  a  rich  woods  of  the  trillium-producing  type,  such  as  a  fertile 
sugar-maple  forest,  one  may  observe  that  the  leaves  in  rotting  sel- 
dom retain  their  form  longer  than  two  years  and  that  the  line  of  de- 
marcation between  the  thin  leaf  litter  of  the  forest  and  the  underlying 
woods  mold  is  sharp  and  clear. 

In  the  sugar-maple  woods  the  decomposition  of  the  leaves  i-  rapid. 
In  the  Maryland  or  kalmia  peat,  as  it  may  he  called  with  more  exact- 
in--,  the  decomposition  i-  slow.  The  cause  of  this  difference  in  the 
rate  of  decomposition  is  the  difference  of  acidity  in  the  two  cases,  and 
this  in  turn  is  dependent  on  the  nature  of  the  leaves  and  of  the  under- 
lying soil,  particularly  whether  the  soil  is  acid  or  alkaline.  A  slight 
alkalinity  in  a  soil  greatly  favors  the  decomposition  of  the  leaves 
overlying  it.  An  acidity  as  strong  as  that  shown  to  occur  in  newly 
fallen  oak  leaves  (see  p.  62)  can  not  help  having  a  pronounced  effect 
in  maintaining  the  acidity  of  the  lower  leaf  layers;  for  it  must  he 
rememhered  that  these  acids  are  soluble  in  rain  water,  ami  are  there- 
fore continually  leaching  down  from  the  upper  through  the  lower 
layers  of  rotting  leaves. 

These  upland  leaf  deposits,  in  which  decomposition  is  retarded  for 
many  years,  the  writer  regards  as  essentially  peat,  and  lo  distinguish 
them  from  hog  peats  he  would  call  them  upland  peats.  An  upland 
peat  may  lie  described  as  a  nonpaludose  deposit  of  organic  matter, 
chiefly  leaves,  in  a  condition  of  suspended  and  imperfect  decompo- 
sition and  still  showing  its  original  leaf  structure,  the  suspension  of 
decomposition  being  due  to  the  development  and  maintenance  of  an 
acid  condition  which  i>  inimical  to  the  growth  of  the  micro-organisms 
of  decay. 

The  use  of  the  name  "  leaf  mold,"  sometimes  applied  to  this  upland 

peal.  -I Ill  lie  restricted  to  the  advanced  stages  in  the  decomposition 

of  leaves,  in  which  leaf  structure  has  disappeared.  True  leaf  mold, 
furthermore,  is  neutral  or  alkaline,  so  far  as  tested. 

When  kalmia  peat  is  to  he  used  for  growing  blueberries  it  should 
he  piled  and  rotted  for  several  months.  An  experience  which  empha- 
sizes the  need  of  this  treatment  is  given  on  page  60.  If  slacked 
as  soon  as  if  is  dug  it  usually  retains  sufficient  moisture  to  carry  the 
rotting  forward,  even  if  the  stack  is  under  cover. 

Kalmia  peat  has  proved  to  he  a  highly  successful  soil  for  growing 
blueberries.  It  has  been  tried  both  pure  and  in  many  mixture-,  as 
will  he  described  in  (he  paragraphs  beginning  on  page  51. 

An  upland  peat  formed  of  the  leaves  of  scrub  pine  (Pinus  virgin- 
iana)  has  also  been  tried  for  blueberry  seedlings.    They  grow  well  in  it. 

Oak  leaves,  it  is  believed,  rotted  for  one  or  two  year-  would  make  a 
good  blueberry  -oil.     In  the  Arlington  National  Cemetery  is  a  ravine 

103 


Bui.   193,   Bu  ,     U    S.  Dept.  of  Agriculture 


Plate  III. 


Fig.  1.— Formation  of  Kalmia  Peat,  Top  Layer. 
Oak  leaves  of  the  preceding  autumn.    (Natural  size.) 


Fig.  2.— Formation  of  Kalmia  Peat,  Second  Layer. 
Kalmia  leaves  of  the  preceding  sumn     i        Natural  size.) 


Bui.   193.   Bureau  of  Plant  Industry.  U.  S.  Dcpt.  of  Agriculture. 


Plate  IV. 


Fig.  1.— Formation  of  Kalmia  Peat,  Third  Layer. 
(ink  leaves 2  years  old.     (Natural  size.) 


Fig.  2.— Formation  of  Kalmia  Peat,  Fourth  Layer. 
Kalmia  leaves  2  years  old,    (Natural  si 


Bui.  193,  Buruau  of  Pa-!  Ii  dustiy   U.  S   Dept.  of  Agriculture. 


Plate  V. 


Fig.  1.— Formation  of  Kalmia  Peat.  Fifth  Layer. 
Mixed  oak  and  kalmia  leaves  3  years  old.    A  few  \i\  of  oak  are  shown,    i  Natural  si/A'.  | 


I    i.  2. -Formation  of  Kalmia  Peat,  Sixth  Layer. 
Mixed  oak  and  kalmia  leaves  I  yearsor  more  old  interlaced  with  live  rootlets  of  oak  and  kalmia. 


\ .  r  J  •  I  I  \    OF    BOGS    vND  SANDY    UPLANDS.  35 

in  which  large  quantities  of  leaves,  chiefly  oak,  have  been  dumped 
for  iM.Mi\  years.  Samples  taken  there  in  laic  November,  L909,  -how 
an  acidity  in  the  case  of  freshly  fallen  leaves  of  0.4  normal :  in  leaves 
apparently  1  year  old,  0.006;  and  in  leaves  aboul  2  years  old,  0 

\  conditi f  great   interest   was   found  in  one  of  these  piles  of 

leaf  mold  which  was  several  years  old.  li  was  mellow  and  black,  and 
the  evidence  of  leaf  structure  had  disappeared.  When  submitted  to 
the  phenolphthalein  test  it  proved  to  be  alkaline,  and  upon  chemical 
examination  it  was  found  to  contain  3.55  percent  of  lime  (CaO). 
In  this  case  decomposition  had  progressed  so  far,  it  is  suggested,  that 
the  lime  in  the  leaves,  remaining  constant  in  amount  and  probably 
having  been  changed  to  a  more  soluble  state,  had  neutralized  the 
remaining  acidity.  The  material,  then  becoming  alkaline,  had  pro- 
ceeded to  decompose  with  greater  rapidity,  until  a  real  mold  had  been 
formed. 

The  condition  here  observed  is  doubtless  the  same  a-  that  which 
occurs  in  the  drained  bog,  <<v  so-called  "muck,"  lands  of  Michigan. 
When  first  plowed  they  will  grow  only  certain  acid-resistant  crops. 
such  a-  buckwheat  or  potatoes,  but  later,  as  their  acidity  disappears, 
they  come  to  attain  a  very  high  degree  of  fertility.  It  is  probably  a 
phenomenon  of  similar  character  w  hich  is  taking  place  in  the  drained 
swamp  lands  of  the  lower  Sacramento  River  in  California,  where  the 
-oil.  which  i>  already  in  a  state  of  remarkable  fertility,  is  becoming 
increasingly  alkaline 

Here  allusion  may  he  made  to  another  phenomenon,  (hat  of  the 
occurrence  of  the  swamp  blueberry  and  certain  other  plants,  such 
a-  the  purple  lady's-slipper  {Cypripedium  acaale)  and  the  swamp 
honeysuckle  {Azalea  nndifora),  in  two  lands  of  -it nation-  one  a 
peat  bog,  the  other  a  sandy,  w  ell  drained,  and  often  dry  upland.  The 
favorite  explanation  of  this  phenomenon  among  botanists  is  that  these 
plant-  are  naturally  adapted  to  the  drier  -it nation  and  that  in  the  bog 
they  find  a  situation  of  "physiological  dryness,"  or  vice  versa. 
A \ '  1 1 i  1  * "  the  existence  of  physiological  dryness  in  peat  bogs  i-  not 
tioned, the  explanation  that  a  bog  plant  finds  an  upland  situation 
congenial  because  it  is  dry  certainly  will  not  answer  for  the  blue- 
berry. It-  occurrence  in  these  two  habitats  is  dependent  on  the 
acidity  of  both  situations.  These  experiment-  have  shown  that  no 
amount  of  dryness  will  make  a  blueberry  flourish  in  an  upland  -oil 
if  that  -oil  i-  not  acid. 

i : 1 1  Fob   v<  u\  i    growth  thi    swamp  blueberri    requires    v  well- aerated  soil. 
Conversely,  rm  swamp  blueberry  does  noi  continui   in   ictivi  growth 

IN     \    SOU     -  v  I  I  i:  v  I  I  l>    WITH     v\  v  I  I  I:. 

In  its  natural  distribution  the  swamp  blueberry  does  not  grow  in 
the  lower,  wetter  type  of  bog.  In  a  typical  leatherleaf  (Ckamae- 
daphm  calyculata)  bog,  for  example,  the  swamp  blueberry   is  found 

103 


36  EXPERIMENTS    IX    BLUEBERRY   CULTURE. 

either  about  the  margin  of  the  bog  or  on  hummocks.  In  both  these 
situations  most  of  the  roots  of  the  blueberry  bushes  stand  above  the 
summer  level  of  the  water.  When  a  bog  has  been  built  up  by  the 
growth  of  vegetation  and  the  accumulation  of  the  debris  until  the 
surface  is  above  the  summer  water  level,  the  swamp  blueberry  will 
occur  generally  over  the  bog. 

An  examination  of  blueberry  plants  occurring  on  hummocks  and 
bog  margins  has  shown  that  such  roots  as  extend  beneath  the  per- 
manent summer  water  level  bear  few  feeding  rootlets  or  none  at  all. 

In  one  experiment  it  was  attempted  to  grow  blueberry  seedlings 
in  water  cultures  containing  various  dissolved  nutrients.  It  was 
found  that  the  roots  made  no  new  growth,  that  the  new  leaves  were 
few  and  small,  and  that  the  general  health  of  the  plants  was  not 
good,  whatever  the  character  of  the  nutrient  substances  in  the  solu- 
tions. It  was  frequently  observed  also  in  the  various  oil  cultures. 
particularly  those  in  undrained  glass  pots,  that  the  continued  satu- 
ration of  the  soil  with  water  reduced  the  root  growth  and  enfeebled 
the  whole  plant.  Continued  excessive  watering  of  potted  blueberry 
plants  was  always  found  injurious. 

The  observations  just  recorded  must  not  be  understood  to  mean 
that  submergence  of  the  roots  is  always  injurious  to  the  swamp  blue- 
berry. In  winter  and  early  spring  the  water  level  of  bogs  containing 
blueberries  often  remains  high  enough  for  several  months  to  com- 
pletely submerge  the  whole  root  system  of  the  plants.  On  the  lower 
end  of  the  Wankinco  cranberry  bog  near  Wareham,  Mass.,  are  some 
native  bushes  of  the  swamp  blueberry,  the  roots  of  which  have  been 
submerged  in  .")  feet  of  water  from  December  to  May  each  year  for 
about  twenty  years.  These  bushes  when  observed  in  September,  L909, 
gave  every  evidence  of  vigor.  Their  twig  growth  was  of  good  length 
and  thickness,  their  foliage  was  dense  and  of  a  healthy  color,  their 
flowering  buds  for  the  next  year  were  fairly  numerous,  and  the  bushes 
were  -aid  to  be  as  productive  of  fruit  as  neighboring  bushes  on  higher 
ground. 

It  would  appear  from  these  facts  that,  while  submergence  during 
the  dormant  period  is  not  injurious  to  the  swamp  blueberry,  its  roots 
dining  their  actively  growing  period  must  be  kept  above  the  water 
level  so  as  to  be  well  aerated. 

(10)  Aeration  conditions  satisfactory  for  the  swamp  blueberry  are  preva- 
lent   l.N    SAND'S    SOILS. 

The  experiment  cited  above  on  this  page  showed  that  blueberry 
seedlings  having  their  roots  suspended  in  nutrient  solutions  failed  to 
make  a  normal  growth  even  though  the  solutions  were  suitably  acidu- 
lated. This  failure  was  ascribed  to  lack  of  aeration.  In  another 
experiment,  described  on  pages  28  and  •_".».  it  was  shown  that  a  similar 
nutrient  solution  when  used  to  water  a  blueberry  plant  potted  in  sand 
produced  a  normal  growth  of  both  idol-  and  stems.  The  sand  l'ur- 
L93 


VTION    CONDITIONS    IN    SAND    AND    PEAT. 

nished  no  appreciable  nourishment  and  the  only  essential  difference 
in  the  two  cases  was  the  abundant  root  aeration  afforded  by  the  sand 
culture.  Sand  i-  therefore  regarded  as  having  been  shown  experi- 
mentally  to  furnish  condition-  suitable  for  soil  aeration. 

In  all  the  experiments  in  which  blueberry  seedlings  were  grown  in 
sand  cultures  suitably  acidulated,  the  root   growth   was  good,  even 
when  very  little  nourishment  was  given  the  plant,  and  when  \\-<\  with 
:i    ueakl\    acid    nutrient    solution  or   with    peat    water  the  sand-pi 
plants  always  made  a  luxuriant  root  growth. 

In  their  wild  state  blueberries  are  especially  prevalent  on  the  sandy 
soils  of  i  lie  Atlantic  Coastal  Plain,  as  well  as  on  sandy  plain-  and  pine 
barrens  in  the  interior.  The  drainage  of  such  soils  is  good  and  their 
aerat  ion   is  excellent. 

(11)  Aeration  conditions  satisfactory    for  thi    swamp  bluebekri    vri    found 

I  \    in:  VINED    I  [BROl  S    PI    VT. 

Kaltuia  peal  when  in  the  original  turf-  or  mat-  i-  full  of  -mall 
root-  of  oak.  kalmia.  and  other  plant-.  In  that  condition  it  i-  remark- 
ably porous  and  well  aerated.  Pieces  of  these  turfs  were  used  with 
great  success  in  the  bottoms  of  pot-,  in  place  of  crock-,  to  afford  drain- 
age. For  a  potting  -oil.  however,  kalmia  peat  can  not  easily  be  used 
until  the  -oil  ha-  been  shaken  from  the  ma--  of  root-  or  ha-  been 
rubbed  through  a  screen.  Even  in  that  condition  the  fragments  of 
leaves  and  rootlet-  make  the  whole  mass  porous.  A  pot  containing 
pure  kalmia  peat  prepared  by  such  rubbing  often  remains  moist,  yet 
well  aerated,  for  day- at  a  time  without  watering.  This  moisture  con- 
dition is  due  to  two  remarkable  properties  of  peat,  it-  ability  to  hold  a 
large  amount  of  water,  and  the  tenacity  with  which  it  clings  to  it. 

Kalmia  peat  taken  from  the  interior  of  a  -tack  after  it  has  remained 
several  month-  under  cover  ordinarily  contain-  loo  per  cent  of 
water,  computed  on  the  dry  weight  of  the  peat.  Even  with  this  very 
high  water  content  a  peal  -oil  i-  in  a  beautiful  condition  id'  tilth. 
mellow,  well  aerated,  and  to  the  sight  and  touch  apparently  only 
moderately  moist.  Ordinary  loam  in  a  similar  condition  contain- 
only  about  Is  per  cent  of  water,  and  -and  aboul  3  per  cent.  When 
saturated  with  water  the  moisture  content  of  kalmia  peat  is  about 
,',i  hi  per  cent  of  it-  dry  weight. 

The  ability  of  peal  to  retain  it-  moisture  depends  in  part  on  the 
gradual  drying  of  the  superficial  layers  and  the  consequent  format  ion 
of  a  mulch,  lnit  more  particularly  i-  it  dependent  on  a  certain  phys- 
ical affinity  that  peat  possesses  for  water.  The  comparative  strength 
of  thi-  water-holding  power  in  different  -oil-  may  he  tested  by  sub- 
jecting them  to  a  powerful  centrifugal  force,  which  tends  to  throw 
the  moisture  out  of  the  -oil.  The  standard  centrifugal  force  used 
i-  a  thousand  time-  the  force  of  gravity.    The  percentage  of  moisture 


38  EXPERIMENTS  IN  BLUEBERRY  CULTURE. 

remaining  in  the  soil  after  this  treatment  is  known  as  the  moisture 
equivalent  of  that  soil.  A  test  of  kalmia  peat  made  by  Dr.  Lyman 
J.  Briggs,  of  the  Bureau  of  Plant  Industry,  the  originator  of  this 
method  of  measurement,  showed  a  moisture  equivalent  of  14:2  per 
cent,  as  compared  with  about  30  per  cent  for  clay,  18  per  cent  for 
loam,  and  2  to  4  per  cent  for  sand. 

From  what  has  been  said  it  is  evident  that  fibrous  kalmia  peat 
has  physical  characteristics  that  allow  the  soil  to  be  amply  aerated. 
while  at  the  same  time  holding  abundant  moisture  for  the  supporting 
of  plant  growth. 

In  this  connection  reference  may  be  made  to  the  influence  of  earth- 
worms on  potted  blueberry  plants.  Late  in  the  winter  of  1908-9 
it  was  noted  that  among  the  blueberry  seedlings  of  1907,  wjiich  had 
been  brought  into  the  greenhouse,  were  several  in  which  the  growth 
was  feeble,  although  others  of  the  same  lot  were  growing  vigorously. 
It  was  noted  also  that  the  soil  in  the  pots  in  which  the  feeble  plants 
were  growing  contained  earthworms,  as  evidenced  by  the  excre- 
ment or  casts  deposited  by  them  on  the  surface.  The  worms 
themselves  were  easily  found  by  knocking  the  earth  ball  out  of  the 
pot,  and  the  soil  was  seen  to  have  been  thoroughly  worked  over  by 
the  worms. 

It  was  supposed  at  first  that  the  soil  (a  mixture  of  peat  8,  -and  1, 
loam  1)  in  the  process  of  digestion  to  which  it  had  been  subjected 
in  passing  through  the  alimentary  canal  of  the  earthworms  might 
have  become  alkaline  and  for  this  reason  injurious  to  the  blueberry 
plants.  When  tested  with  phenolphthalein,  however,  the  soil  in  the 
pots  containing  earthworms  and  feeble  plants  was  found  to  be  of  the 
same  acidity  as  that  in  the  pots  containing  no  earthworms  and  with 
vigorously  growing  plants.  Furthermore  tin1  fresh  casts  themselves 
were  of  a  similar  degree  of  acidity. 

The  texture  of  the  soil,  however,  in  the  pots  containing  worms  was 
very  different  from  that  in  the  others.  It  was  plastic,  very  fine 
grained,  almost  clayey,  the  organic  portion  having  been  very  finely 
ground  evidently  in  passing  through  the  gizzard  and  other  digestive 
apparatus  of  the  earthworms.  The  aeration  of  the  soil  in  this  condi- 
tion must  have  been  far  poorer  than  in  the  coarser  soil  containing  a 
large  amount  of  leaf  fragments  not  worked  over  by  worms,  and  it 
may  be  that  the  difference  in  growth  of  the  blueberry  plants  was  due 
to  the  difference  in  aeration.  It  i>  not  by  any  means  certain,  however, 
that  the  plants  in  the  pots  containing  earthworms  may  not  have  been 
injured  directly  through  (lie  eating  of  (heir  rootlets  by  the  worm-. 

(12)    AlCKATION    CONDITIONS    SATISFACTORY    FOR    Till     SWAMP    BLUEBERRY    A.RE    FOUND 
IN    MASSES   hi     LIVE,    MOIST.   BUT   NOT  SUBMERGED   SPHAGNUM. 

In  some  swamps  the  water  level  remains  permanently  above  the 
general  surface  of  the  ground.     \M»en  the  swamp  blueberry  occurs 

L93 


DERATION    CONDITIONS    IN    SPHAGNUM.  39 

in  such  situations  ii  grows  on  hummocks  the  summits  of  which  stand 
nbove  the  water  during  the  growing  season.  Unless  the  water  level 
[s  extremely  variable  or  the  ground  is  densely  -haded,  these  hum- 
mocks are  usually  covered  with  a  cushion  of  live  sphagnum  moss.  Ii 
is  a  peculiarity  of  t  hi-  moss  thai  ii  absorbs  water  \\  iili  great  avidity; 
indeed,  sphagnum  is  one  of  the  most  absorbent  substances  known.  If 
one  end  of  n  nearly  dry  branch  of  sphagnum  is  brought  into  contacl 
wnli  a  little  water,  the  whole  branch  becomes  wet  almost  instantly. 
The  water  rushes  along  with  marvelous  rapidity  through  the  cells 
of  the  plant  and  especially  through  the  interstices  between  the  minute 
overlapping  leaves.  The  white  air  spaces  between  the  half  dry  leaves 
flash  "in  of  existence  one  after  the  other  like  candle  flames  in  a  gust  of 
wind.  The  same  ability  to  absorb  water  is  characteristic  of  masses  of 
tin-  plant.  If  the  lower  part  of  a  cushion  of  sphagnum  is  in  contact 
with  i'vi'c  water  the  fluid  is  conveyed  from  stem  to  branch  and  front 
plant  to  plant  in  sufficient  amount  to  render  the  whole  mass  a-  wet  as 
a  sponge.  When  one  squeezes  a  handful  of  such  moss  taken  perhaps 
a  foot  or  more  above  the  source  of  moisture  the  water  runs  out  in 
streams.  A  -ample  of  live  sphagnum  with  less  moisture  than  usual 
but  -till  with  enough  to  maintain  itself  in  a  growing  condition  was 
found  to  contain  991  per  cent  of  water,  computed  on  the  dry  weight 
of  the  sphagnum,  while  saturated  live  sphagnum  carried  1,005  pet- 
cent  of  water.  On  the  basis  of  it-  dry  weight,  therefore,  sphagnum 
contain-  about  ten  times  as  much  water  as  peat,  which  it-elf  contains 
about  six  time-  a-  much  a-  ordinary  loam  ami  about  thirty-five  times 
a-  much  a-  -and. 

The  innumerable  extracapillary  air  -pace-  between  the  branches  of 
sphagnum  plant-  and  between  the  plants  themselves  furnish  good 
aeration,  even  when  the  individual  branches  are  saturated  with  water. 
When  the  moisture  i-  less  the  aeration  i-  -till  better.  The  cushion  of 
sphagnum  on  a  hummock  tend-  to  build  itself  up  by  the  gradual 
process  of  growth  and  decay  to  the  maximum  height  to  which  it  can 
con\e\  the  large  amount  of  water  required  for  its  growth,  and  an 
increasing  degree  of  aeration  i-  found  from  the  water  line  upward. 

II'  the  sphagnum  cushion  on  a  blueberry  hummock  i-  examined  the 
whole  ma—  will  he  found  interlaced  with  the  minute  rootlets  id'  the 
blueberry,  far  above  the  level  of  the  nnderh  ing  soil.  The  conditions 
•  'I  permanent  moisture  and  thorough  aeration  found  in  these  sphag- 
num cushions  seem  to  be  almost  ideal  for  the  development  of  blueberry 
roots. 

It  must  not  he  assumed  that  the  vigorous  growth  of  blueberry 
root-  in  sphagnum  i-  due  to  anj  high  nutritive  quality  of  the  sphag- 
num it-elf.  Such  a  conclusion  would  be  erroneous.  When  set  out 
in  sphagnum  and  watered  with  tap  water,  blueberry  plant-  remain 
healthy  and  develop  a  ven   large  i<>>\  system,  but  the  stems  do  not 

193 


40 


EXPERIMENTS   IK    BLUEBERRY    (TLTURE. 


grow  as  luxuriantly  as  when  the  plants  are  in  a  peat  soil.  From 
experiments  with  the  growing  of  blueberries  in  sand  watered  with 
peat  water  it  is  known  that  such  water  furnishes  the  food  materials 
necessary  for  vigorous  growth.  It  is  reasonable  to  conclude,  there- 
fore, that  the  chief  nourishment  of  a  blueberry  plant  growing  on  a 
pure  sphagnum  hummock  comes  from  the  bog  water  sucked  up  by 
the  sphagnum  and  not  from  the  sphagnum  itself. 

PECULIARITIES  OF  NUTRITION. 

(13)  The  swamp  blueberry  is  devoid  ok  root  hairs,  the  minute  organs 
through  which  the  ordinary  plants  of  agriculture  absorb  their 
moisture  and  food. 

The  structure  of  the  rootlets  of  ordinary  agricultural  plants  may 
be  understood  by  reference  to  figures  11  to  13,  which  illustrate  these 
organs  as  they  occur  in  a  wheat  seedling  germinated  between  layers 
of  moist  blotting  paper.     Attention  is  directed  particularly  to  the 


Fig.  11. — Root  of  a  wheat  plant,  showing  die  root  hairs.     (Natural  size.) 
Fir,.  12.— Portion  of  a  wheal  root,  with  rool  hairs.     (Enlarged  10  diameters  I 
FIG.  13. — Tip  of  the  root  hair  of  a  wheat   plant.      (Enlarged   1. I  diameters.) 

root  hairs.  It  will  be  observed  that  the  wall  of  the  root  hair  is  very 
thin,  appearing  in  optical  section  as  a  mere  line  with  barely  measur- 
able thickness, even  when  highly  magnified.  Furthermore,  the  sur- 
face area  of  the  root  hairs  is  many  times  greater  than  that  of  the  root 
itself.  The  chief  function  of  these  root  hairs  is  to  absorb  for  the 
use  of  the  plant  the  soil  moisture  and  the  plant-food  materials  dis- 
solved in  it,  a  function  which  the  root  hairs  are  enabled  to  perform 
with  great  efficiency  because  of  the  two  characteristics  just  men- 
tioned— their  large  surface  area  and  the  thinness  of  their  walls. 

The  rootlets  of  the  blueberry  are  remarkable  in  having  no  root 
hairs  whatever,  as  may  lie  seen  by  reference  to  figures  1  I  to  Hi.  The 
walls  of  the  superficial,  or  epidermal,  cells  of  the  rootlets  are  thick. 
measuring  0.00005  to  0.0001  of  an  inch  (  L.3  to  •_'.:•  ft,),  while  the  walls 
of  the  root  hairs  of  wheal  are  one-fourth  to  one-sixth  as  thick, 
so  thin,  in   fact,   that  they  could  be  measured   only   with   difficulty 

193 


l;i  Dl  I  I  l'   ABSORPTIVE   Si  R]   \<  I     0]     BLUEBERRY     ROOTS. 


II 


even  when  enlarged  5,900  diameters.  Notwithstanding  the  fact, 
therefore,  thai  the  bluebern  roots  are  fine  and  numerous,  their 
actual  absorptive  capacity  would  appear 
to  be  small,  in  consequence  of  the  absence 
of  root    hail-. 

It  is  found  by  a  computation  thai  a  sec- 
tion of  a  blueberry  toot  let  having  no  root 
hairs  presents  about  one  tenth  the  absorp- 
tive surface  of  an  equal  area  of  a  wheat 
rootlet  bearing  root  hairs,  and  the  thick- 
ness of  the  surface  membranes  in  the 
wheat  i-  certainly  not  more  than  a  quarter  fig.  it.  Root  of  a  biu< 
that    in  the  blueberry.     Furthermore,  the  plant    <Natllralsize> 

blueberry  rootlet  grows  only  about  0.04  inch  (1  mm.)  a  day  under 
favorable  conditions,  while  the  wheat  rootlet  often  grows  twenty 
time-  as  fast.  In  all  this  provision  for  rapid  food  absorption  in  the 
one  plant    and   retarded   absorption  in  the  other  we  find  a   reason    for 


Pro.    l"      Bool    of   :\    blueberry    plant.      (Rnli 
i ii  diameters.  > 


Fig.      16.     Blueberry      rootlel 
i  Enlarged  100  diameters.  I 


the  comparatively  verj  slow  rate  of  stem  growth  thai  characterizes 
the  blueberry  plant.  The  importance  of  -low  root  absorption  and 
the  danger  to  which  these  plant-  would  be  subjected  if  their  roots 
absorbed  water  rapidly  are  discussed  on  page  50. 


103 


42  EXPERIMENTS   IN    BLUEBERRY   CULTURE. 

The  young  rootlets  of  the  blueberry  before  they  branch  are  ex- 
ceedingly slender,  varying  from  0.002  to  0.003  of  an  inch  (50  to  75  fi) 
in  diameter.  This  makes  them  very  susceptible  to  actual  drying  and 
they  are  easily  killed  by  it.  This  characteristic  has  an  important 
healing  on  the  treatment  of  these  plants  when  in  pots.  The  matter 
is  discussed  on  pages  65  to  67. 

(14)  The  rootlets  of  healthy  plants  of  the  swamp  blueberry  are  inhab- 
ited BY  A  FUNGUS,  OF  THE  SORT  KNOWN  TECHNICALLY  AS  AN  ENDOTROPHIC 
MYCORRHIZA.0 

As  already  stated,  the  ultimate  rootlets  of  the  blueberry  are  very 
fine,  their  diameter  varying  from  0.002  to  0.003  of  an  inch  (50  to  75  ft). 
In  rootlets  of  the  smaller  size  about  three  rows  of  epidermal  cells  are 
visible  in  a  lateral  view,  in  the  larger  rootlets  about  five  rows.  In  a 
newly  grown  rootlet  not  contaminated  with  soil  particles  these  epi- 
dermal cells,  and,  indeed,  all  the  underlying  cells  as  well,  are  as  trans- 
parent as  glass,  and  were  it  not  for  the  difficulties  due  to  the  refrac- 
tion of  light  the  examination  of  the  contents  of  the  cells  would  not  be 
difficult.  As  a  matter  of  fact  the  study  of  the  contents  of  the  live 
cells  is  difficult,  their  intelligent  examination  requiring  the  use  of  an 
oil  immersion  objective  and  microscopic  enlargements  of  1,000  to 
1,500  diameters.  The  darkened  window  installation  for  a  microscope, 
devised  by  Dr.  X.  A.  Cobb,  of  the  Bureau  of  Plant  Industry,  and 
used  in  his  laboratory,  has  been  found  almost  indispensable  in  this 
work. 

(lean  rootlets  may  be  procured  readily  from  active  blueberry 
plants  in  the  open  spaces  between  half-rotted  leaf  blades,  in  clean 
sand,  in  live  sphagnum,  or  at  the  outer  surface  of  the  ball  of  soil  in 
earthen  pots.  Rootlets  taken  from  live  sphagnum  are  especially  clean. 
They  are  conveniently  studied  when  simply  placed  in  water  on  a 
microscope  slide  under  a  thin  cover  glass  held  in  place  by  a  ring  of 
paraffin. 

Ordinarily  the  only  thing  visible  in  one  of  the  live  epidermal  cells  is 
the  minute  cell  nucleus  lying  close  to  (he  cell  wall.  The  protoplasmic 
membrane  lining  the  cell  is  very  thin  and  is  invisible  except  where  it 
is  thickened  to  envelop  the  nucleus.  The  remainder  of  the  cell  is 
tilled  with  the  colorless  cell  sap.  An  examination  with  medium  en- 
largements will  show  some  of  the  cells  faintly  clouded  in  appearance. 
A  higher  power,  such  as  is  afforded  by  a  2-mm.  oil  immersion  objec- 
tive and  a  l'.'-niin.  eyepiece,  with  proper  illumination,  will  resolve  the 
cloudiness  into  a  mass  of  fungous  threads,  or  hyphse.  These  may  he 
few.  making  only  two  or  three  irregular  turns  about  the  interior  of 
the  cell,  as  occasionally  found,  or  they  may  be  more  numerous,  even 
occupying  the  whole  sap  space,  as  shown  in  figure  17,  in  a  dense  knot 

"The  spelling  mycorhiza  is  also  in  good  standing  and  is  used  in  many  German, 
English,  and  American  botanical  works. 
193 


ftOOl    FUKGUS  0]     mi     B]  I   i  Bl  RRY, 


I.; 


of  interwoven  and  irregular  snakelike  coils.    These  hyphae  arc  aboul 
0.0 16  i"  0.1 L2  of  an  inch  (  L.5  to  3  fi)  in  diameter. 

On  the  onici-  surface  of  the  cells  containing  these  fungous  threads 
others  of  similar  or  a  little  greater  thickness  may  be  observed.  Some 
tin it-^  thi'v  are  transparent  and  their  detection  requires  the  same  high 
power  of  ili>'  microscope  as  do  those  in  the  interior  of  the  cells. 
Sometimes,  however,  these  exterior  threads  have  a  pale-brown  color 
and  arc  then  readily  seen.  Their  surface  is  smooth,  devoid  of  mark- 
ings of  anj  kind.  Ordinarily  the 
thread  wanders  loosely  along  the  sur- 
face of  the  root  gn  ing  off  an  occa 
sional  branch  and  having  an  occa- 
sional septum.  Sometimes  the 
threads  and  their  branches  maj  form 
an  open  network  about  the  rootlet. 
but  they  never  form  a  dense  sheath  of 
hyphae  such  as  is  characteristic  of  the 
mycorrhiza  of  t  he  oak. 

The  connection  between  the  exter- 
nal and  the  internal  hyphae  is  not 
ea-\  i.i  see  at  a  single  observation, 
for  the  passage  of  the  hyphae  through 
the  eell  wall  i-  rarely  caughl  in  op- 
tical section,  and  even  then  a  clear 
observation  is  usually  rendered  diffi- 
cult because  of  refraction.  A  very 
clear  case,  however,  was  observed  in  a 
runt  let  of  laurel  (Kalmia  latifolia),a 
shrub  which  ha-  a  mycorrhiza!  fun- 
gus similar  to  that  of  the  blueberry. 
A  drawing  of  that  specimen  is  shown 
in   (inure   Is. 

The  passage  of  the  fungus  through 
the  cell  wall  may  frequently  lie  ob- 
served in  the  blueberry  by  first  focus- 
ing on  the  external  hypha  at  a  point 
where  it  appear-  to  have  a  lateral  hump  or  a  very  short  branch,  and 
then  focusing  slowlj  downward.  In  thi-  wax  one  pa  se  from  the 
external  to  the  internal  part  of  the  fungus,  having  had  some  portion 
of  the  intervening  hypha  continuously  in  view.  The  hypha  always 
appears  much  constricted  at  the  point  where  it  goes  through  the 
cell    wall. 

Thi-  fungus  is  of  the  type  named  bj   Frank  in  1  vv7  an  endotrophic 
mycorrhiza  to  distinguish   it    from  an  ectotrophic  mycorrhiza,  such 

L93 


Pig.  it.  Mycorrhiza!  fungus  of  a  blue- 
berry plant  densely  crowded  In  two 
epidermal  cells  of  the  rool .  i  En- 
larged aboul    1,2 Ilami 


44 


EXPERIMENTS  IN    BLUEBERRY   CULTURE. 


as  occurs  on  the  roots  of  oaks.  In  the  latter  type  of  mycorrhiza  the 
hyphse  of  the  fungus  form  a  dense  sheath  around  the  rootlet,  com- 
pletely shutting  it  off  from  direct  contact  with  the  surrounding  soil. 
The  loose  hyphse  on  the  outside  of  the  sheath  resemble  root  hairs 
and  it  is  supposed  to  be  a  part  of  their  function  to  absorb  soil  mois- 
ture and  transmit  it  to  the  oak  rootlet  just  as  root  hairs  do. 

It    has  not   yet  been  possible,  for  want  of  time,  to  study  the  life 
history  of  this  mycorrhiza!  fungus  of  the  blueberry.    There  i-.  how- 
ever, a  clew  to  its  identity  in  the  work 
of  Miss   Charlotte  Ternetz,   Ph.   D., 
described  on  page  !'.». 

The  experiments  thus  far  made  do 
not  warrant  a  supposition  that  any 
good  peat  soil  requires  inoculation 
with  the  mycorrhiza!  fungus  before 
blueberry  plants  will  grow  well  in  it. 
The  fungus  appears  either  to  he  al- 
ready in  the  soil  or  to  accompany  the 
seeds  when  they  are  sown  in  it. 

(15)  The    mycorrhizal    fungus    of    the 

.sWAMP  BLUEBERRY  Al'PI  \i;s  TO  HAVE 
Nu  INJURIOUS  EFFECT,  BUI  EATHEB  \ 
BENEFICIAL  EFFECT,  UPON  Till';  BLUE- 
BERRY   PLANT. 

The  epidermal  cells  in  which  the 
mycorrhiza]    fungus    occurs    are    not 

swollen  nor  distorted,  nor  do  their 
contents  collapse  or  show  any  of  the 
other  effects  usually  produced  by 
pathological  fungi.  They  appear  to 
differ  in  no  respect  from  other  epi- 
dermal cells  of  the  blueberry  rootlets. 
In  rapidly  growing  rootlets  the  fun- 
gus seems  not  to  be  able  to  keep  pace 
with  the  rootlet  itself  and  may  not 
occui-  for  a  considerable  distance  bach 
from  the  growing  tip.  The  fungus-filled  cells  ordinarily  are  most 
numerous  on  certain  small,  short,  and  crooked  lateral  rootlets  the 
growth  of  which  is  slow.  When  root  growth  of  a  vigorous  plant  i< 
retarded  or  becomes  even  stagnated,  the  fungus  may  invade  the  epi 
dermal  cells  to  the  very  apex.  Sometimes  half  the  cells  in  such  a 
rootlet  are  gorged  with  fungi,  yet  the  delicate  cell  walls  --how  no 
displacement  or  distortion.  There  is  no  indication  whatever- that 
the  fungus  causes  any  pathological  disturbance  or  is  in  any  way 
obnoxious    to    the    plant.     On    the    contrary,    the    uniformity    with 

L93 


Fig.  is. — Mycorrhiza]  fungus  of  Kal- 
niin  latifolia  in  an  epidermal  cell  of 
the  root:  a,  Cell  walls  ;  b,  external 
hypha?  of  the  mycorrhiza!  fungus; 
c  internal  hyphse;  <i.  point  of  pene 
tration  or  the  cell  \\;ill  bj  the 
mycorrhizal  fungus.  (Enlarged 
ahoul  1,000  diameters,  i 


DEFICIENCY  OF    NITRATES   IN    BLUEBERRY    SOILS.  15 

which  it  has  been  found  to  occur  <>n  healthy  plants  and  its  frequent 
absence  or  scarcity  on  sickly  plants  are  Fad  suggestive  of  :i  bene- 
ficial influence.  The  nature  of  t hi^  beneficial  influence  is  discussed 
en  pages   Is  to  50. 

(16)  THl      m  ii>    n   \  1  -i     SOILS   IN     H  II  li  II     l  III     SWAMP   BLU1  .  ii:i\  i  s     \i;i     DE- 

FICIENT IN  "available"  nitrogen,  although  containing  largi    amounts 

hi     "     Mi\  AVAILABLE  "    NITBOG1  N. 

Ordinai'y  agi'icultural  plants  absorb  their  nitrogen  from  the  soil 
in  the  form  <>l'  nitrates.  Whether  any  arc  able  i<>  utilize  directly 
other  forms  "I'  nitrogen,  particularly  ammonia  nitrogen,  has  been  the 
subject  <>!'  much  experiment  and  of  discussion  by  many  authors.  It 
is  tine  in  general,  however,  that  the  common  plants  of  agriculture 
when  their  other  food  requirements  are  satisfactory  make  their 
growth  in  direct  proportion  to  their  ability  to  secure  their  nitrogen 
in  the  form  of  nitrate-.  For  this  reason  the  processes  of  agriculture 
are  largely  devoted  to  the  securing  and  maintenance  of  conditions 
that  will  bring  about  the  transformation  of  nonavailable  nitrogen 
into  nitrates.  Soil-  in  which  tin-  can  not  lie  done  without  great 
expense  in  proportion  to  their  productiveness  are  generally  con- 
sidered poor. 

The  acid  -oils  in  which  wild  blueberries  thrive  an-  always  looked 
upon  as  infertile  in  their  natural  -tale,  and  unless  these  <oils  are 
extensively  manipulated  cultivated  plant-  do  not  do  well  in  them. 
Whether  or  not  a  pari  of  this  infertility  i-  due  to  the  directly  injuri- 
ous effect  of  acid  or  other  poisonous  substances,  it  is  known  that  the 
conditions  existing  in  these  soils  are  directly  antagonistic  to  the  for- 
mation of  nit  rale-,    i  See  \>.    17.  i 

Thai  kalmia  peal,  the  -oil  found  in  these  culture-  to  he  most  suc- 
cessful  for  blueberries,  i-  deficient  in  nitrates,  although  containing  an 
abundance  of  nitrogen  in  other  form-,  is  shown  by  the  following 
mi  rogen  determinal  ion   : 

rOTAl      NITROGEN     IN     KALMIA    I'l.  \  I'. 

( Determinations  made  by  .Mr.  T.  < '.  Trescott.) 
Sample. 

I 
o 


IVr 

cenl 

1. 

i>; 

1. 
1. 

Is 

in 

1. 
1. 

to 

12 

Average  of  total  alt  rogen  1.  iii 


IlKi 


46  EXPEBIMENTS  IN  BLUEBERRY  CULTURE. 

NITROGEN    IN    KALMIA   PEAT  IN  THE  FORM   OK  NITRATES. 

(Determinations  made  by  Mr.  Karl  I'.  Kellerman.) 
Sample.  Per  cent. 

7 0.0012 

8 .0022 

» . .  0008 

10 .0013 

11 .0025 

12 .in  i«  is 

Average  of  nitrate  nitrogen .0015 

(17)  The  deficiency  of  available  nitrogen  in  the  acid  peaty  soil  in  which 
the  swamp  blueberry  grows  best  is  due  to  the  inability  of  1111  nitri- 
fying bacteria  to  thrive  in  such  a  soil  because  of  its  acidity. 

Iii  order  to  understand  the  conditions  antagonistic  to  nitrification 
which  exist  in  good  blueberry  soils  it  is  necessary  first  to  discuss  the 
source  and  transformation  of  nitrogen  in  ordinary  soils. 

The  available  nitrogen  in  the  soil,  such  as  is  absorbed  by  an  ordi- 
nary plant,  is  commonly  derived,  unless  fertilizers  have  been  ap- 
plied, from  the  decomposition  of  the  humus  contained  in  the  soil, 
and  the  humus  is  itself  a  product  of  the  decomposition  of  plant  and 
animal  remains.  These  remains  consist  ordinarily  and  chiefly  of  the 
partially  rotted  leaves,  stems,  and  roots  of  plants. 

In  the  older  agricultural  literature  the  name  humus  was  applied 
to  a  particular  kind  of  soil  which  is  more  properly  covered  by  the 
terms  vegetable  mold,  leaf  mold,  and  woods  mold.  (See  |>.  24.) 
Later  the  application  of  the  word  humus  was  restricted  to  that  por- 
tion of  a  soil  consisting  of  the  plant  and  animal  remains,  in  whatever 
stage  of  decomposition.  The  proper  designation  of  these  remains  is, 
however,  organic  matter.  In  the  sense  just  described  the  word  humus 
is  still  frequently  used,  but  not  with  correctness  and  precision. 
Humus,  as  now  understood  by  agricultural  chemists,  represents  a 
stage  in  the  decomposition  of  organic  matter  in  which  the  cellular 
structure  has  wholly  disappeared  and  (he  original  substance  IS  or  at 
-nine  stage  has  been  entirely  dissolved. 

Since  it  is  often  necessary  to  allude  to  organic  matter  in  the  earlier 
stage,  as  distinguished  from  organic  matter  as  a  whole,  which  in- 
cludes the  humus  stage  as  well,  the  term  cellular  organic  matter,  or. 
more  simply  still,  cellular  matter,  is  suggested  as  a  convenient  desig- 
nation. In  cellular  matter  the  cellular  structure  of  the  animals  or 
plants  still  remains  and  may  be  detected  either  by  the  eye  or  by  the 
microscope. 

Humus,  which  is  a  complex  mixture  of  diverse  substances,  does  not 

ordinarily  exist    in   the  soil    in   a   dissolved   condition,  but    i-   usually 

combined  with  lime  or  magnesium.     The  resultant  compounds,  often 

indiscriminately  blanketed  under  the  names  calcium  ami  magnesium 

103 


BUMUS  THE  USUAL  SOURC]     01     NITRATES.  1  i 

humate,  are  not  soluble  in  water,  but  form  :i  usually  black  precipitate, 

w  hull  gi\  es  a  dark  color  to  the  -nil. 

To  extracl  it-  humus  a  -oil  is  first  washed  with  dilute  acid,  by 
which  the  lime,  magnesium,  or  other  humus  precipitating  substance  is 
dissolved  and  leached  away.  The  humus  itself  is  then  removed  from 
the  -"il  l>v  long-continued  washing  with  a  weal;  solution,  commonly 
I  per  cent,  of  ammonia.  Upon  the  application  of  this  treatment  to 
kahiiia  peal  an  inky-black  extract  is  secured.  When  this  is  evap 
orated  to  dryness  the  residue  i-  a  black  substance  which  when  scraped 
from  the  dish  resembles  coal  dust  or,  even  more  closely,  burned  sugar. 
This  substance  is  one  of  the  forms  of  humus.  It  absorbs  water  read- 
ily, assuming  the  texture  of  thin  jelly.  It  has  ;i  somewhat  sooty  odor 
and  taste.  It  dissolves  in  water,  the  solution  being  acid  in  reaction. 
A  liter  of  water  in  which  had  been  dissolved  a  gram  of  humus  ex 
tracted  from  kahnia  peat  showed  when  tested  ;i  0.002  normal  acidity. 
Such  ;i  solution  is  Mack  unless  viewed  in  a  thin  layer,  and  when 
ill  luted  tn  10,000  c.  c.  it  has  a  brown  color  similar  to  that  of  ordinary 
cider  vinegar.  II'  lime  is  added  to  the  solution  the  humus  unite-  with 
it  and  is  thrown  down  as  a  black  precipitate,  leaving  the  liquid  clear. 
As  stated  in  the  preceding  paragraph,  it  is  in  such  a  precipitated  and 
neutral  or  alkaline  form  that  humus  ordinarily  occurs.  The  charac- 
teristic brown  color  of  the  water  in  bogs  indicate-  an  acid  condition. 
the  presence  of  humus  in  solution,  and  the  absence  of  soluble  lime. 

The  process  of  decomposition  by  which  cellular  matter  i-  trans- 
formed into  humus,  in  which  the  cellular  structure  has  entirely  dis- 
appeared, is  know  n  as  humificat  ion. 

Humus  contain-  nitrogen,  but  the  nitrogen  is  not  in  the  form  of 
nitrate-  and  therefore  can  not  be  assimilated  by  ordinary  plant-. 
The  transformation  of  humus  nitrogen  into  nitrates  occur-  during  a 
further  process  of  decomposition  known  as  nitrification. 

The  nitrification  of  humus  is  brought  about  by  certain  bacteria 
which,  growing  in  the  humus-laden  soil  under  suitable  conditions, 
produce  first  ammonia,  then  nitrites,  and  then  nitrate-.  In  artificial 
culture-.  In  addition  to  proper  condition-  of  temperature,  moisture, 
and  good  aeration,  these  nitrifying  bacteria  require  for  vigorous 
growth  a  neutral  or  slightly  alkaline  medium.  In  a  distinctly  acid 
medium  the  nitrifying  bacteria  gro^  little  or  not  at  all. 

In  order  to  ascertain  the  degree  of  nitrification,  if  any,  taking  place 
in  kalmia  peat,  a  -eric-  of  nitrification  tests  of  this  material  was  made 
by  Mr.  Karl  I-'.  Kellerman.  These  tests  showed  that  neither  in  fresh 
peat  nor  in  peat  rotted  for  three  month-  was  nitrification  in  progress, 
but  when  the  acidity  of  the  peat  was  neutralized  l>\  the  addition  of 
lime  nitrification  l  tega  n, 

193 


48  EXPERIMENTS  IN  BLUEBERRY  CULTURE. 

(  18)   From  the  evidi  \<  i    vi   hand  the  presumption  is  that  the  mycorrhizal 

I  CJNGTJS  01  nil  SWAMP  BLUEBERRY  TRANSFORMS  THE  NONAVAILABLE  NITRO- 
GEN OF  PEATY  SOILS  INTO  A  FORM  OF  NITROGEN  WAILABLE  FOR  THE  NOUR- 
ISHMENT   OF    THE    BLUEBERRY    PLANT. 

It  is  a  well-established  principle  of  plant  physiology  that  (with  the 
possible  exception  of  a  few  bacteria)  those  plants  which  contain  no 
chlorophyll,  the  green  coloring  matter  of  leaves,  are  unable  to  grow 
with  mineral  nutrients  alone,  since  they  are  unable  to  manufacture 
their  own  carbohydrates.  Plants  without  chlorophyll,  including  the 
fungi,  are  dependent  for  the  fundamental  part  of  their  nourishment 
on  the  starch  or  other  related  carbohydrates  originally  elaborated 
from  carbon  dioxid  and  water  by  the  chlorophyll-bearing  plants. 
They  also  differ  from  the  higher  plants  in  being  able  to  supply  their 
nitrogen  requirements  directly  from  organic  nitrogen  compounds. 

Fungi  may  be  directly  parasitic  on  a  chlorophyll-bearing  plant,  as 
in  the  case  of  the  mildew  fungus  of  rose  leaves,  or  they  may  grow  on 
substances  derived  from  chlorophyll-bearing  plants,  such  as  bread 
or  jelly. 

Fungi  are  particularly  abundant  in  the  decaying  vegetable  matter 
forming  the  leaf  litter  of  a  forest,  even  though  this  litter  may  be 
distinctly  acid  in  its  chemical  reaction.  They  are  known,  indeed, 
to  grow  luxuriantly  on  vegetable  remains  containing  no  nitrates  and 
of  such  acidity  that  nitrification,  or  (he  conversion  of  the  humus 
nitrogen  into  nitrates  by  means  of  bacteria,  can  not  take  place. 

That  the  mycorrhizal  fungi,  like  other  fungi,  are  able  to  extract 
nitrogenous  food  from  the  nonnitrified  organic  matter  with  which 
their  external  portions  are  in  contact  is  a  reasonable  supposition.  It 
is  furthermore  a  reasonable  supposition  that  the  blueberry  plant  is 
able  to  absorb  nitrogenous  material  from  the  internal  portion  of  its 
mycorrhiza;  for  we  know  that  the  clover  plant  is  able  to  absorb  nitro- 
gen under  essentially  (he  same  conditions  from  the  nitrogen-fixing 
bacteria  growing  in  its  root  tubercles. 

To  establish  by  direct  experiment  the  ability  of  the  mycorrhizal 
fungus  of  the  blueberry  to  act  ii.  accordance  with  the  supposition 
outlined  above,  the  fungus  should  be  separated  from  the  plant  and 
grown  by  itself  in  suitable  nutrient  media.  Preliminary  trials  were 
made  to  isolate  the  fungus,  but  without  success,  and  a  lack  of  time 
has  prevented  thus  far  the  pursuit  of  that  branch  of  the  experiments. 

(19)  ll  IS  POSSIBLE  THAT  THE  MYCORRHIZAL  FUNGUS  OF  THE  SWAMP  BLUEBERRY 
TRANSFORMS  THE  FREE  NITROGEN  OF  THE  ATMOSPHERE  INTO  A  FORM  OF 
NITROGEN    SUITED  TO    Till     LSI     ul     THE  BLU/EBERRY  PLANT. 

The  fact  of  the  fixation  of  atmospheric  nitrogen  by  the  bacteria 
inhabiting  the  root  tubercles  of  clovers  is  now  well  known,  and  we 
are  able  to  understand  how  the  abundant  nitrogen  of  the  air.  unavail- 

193 


•nil      ^.TMOSPHER]      \s    \    SOURCE    OF    NITROGEN.  49 

able  for  the  direci  nutrition  of  ordinary  plants,  is  made  available  for 
the  use  of  leguminous  crops. 

It  is  nol  so  generally  known  thai  there  are  in  soils  certain  sp< 
of  bacteria  noi  connected  with  the  roots  of  plants  which  also  po 
the  faculty  of  taking  up  the  nitrogen  oi  the  air  and  making  ii  over 
into  plant  food.     'The  extent  of  the  distribution  of  these  organisms  and 

the  an n<  of  nitrogen  fixation  effected  by  them  are  not  fully  known. 

hui  the  facl  that  such  action  does  take  place  and  that  the  bacteria 
causing  it  occur  in  many  localities  has  been  well  established  by  the 
experiments  i  !'  several  investigators.  The  bacteria  of  this  class  most 
fully  investigated  are  Clostridium  pasteurianum,,  Azotobacter  chro- 
»///.  and  several  other  species  of  this  hitter  genus. 

It  has  been  shown  also  that  certain  fungi,  such  as  Penicillium 
glaucum-,  possess  this  same  power  of  assimilating  atmospheric 
nit  rogen. 

After  the  writer  had  discovered  the  mycorrhizal  fungus  of  the 
swamp  blueberry  in  December,  L907,  and  while  he  was  making  obser 
vations  on  it.  his  attention  was  called  to  the  work  of  Miss  Charlotte 
Ternetz  on  the  mycorrhizal  fungi  of  certain  related  European  plants. 
Miss  Ternetz  published  in  L904  a  paper"  in  which  she  made  the  pre- 
liminary announcement  that  a  fungus  isolated  from  the  root-  of  the 
European  cranberry  (Ox\  oxycoccus)  had  developed  pyenidia 

and  i  hat  t  he  my  eel  i  um  produced  from  spores  from  these  pyenidia  when 
grown  ina  nitrogen-free  nutritive  solution,  bui  with  full  access  to  air, 
showed  upon  analysis  that  it  had  assimilated  free  atmospheric  nitro- 
gen to  the  extent  of  0.6  per  cent  of  the  dry  weight  of  the  mycelium. 
'The  fungus  consumed  only  one-eighth  as  much  dextrose  in  assimi- 
lating  a  given  amount  of  nitrogen  as  was  consumed  by  Clostridium 
■  "',,,.  Similar  hut  not  identical  fungi  were  isolated  from 
other  related  plants. 

In  1907,  in  a  more  detailed  account  of  her  investigations,8  Miss 
Ternetz  described,  a-  new  species  of  Phoma,  live  pyenidia-bearing 
fungi  bred  from  the  roots  of  the  European  cranberry  (Oxycoccus 
oxycoccus),  the  marsh  rosemary  (Andromeda  polifolia),  two  species 
of  heather  (  Eri<  <'  t,  tralix  and  E.  <  ai  i>,  a  >.  and  the  mountain  cranberry 
(Vaccinium  vitisidaea).  She  was  unable  to  demonstrate  absolutely 
that  these  fungi  were  identical  with  the  endotrophic  mycorrhiza  of 
the  host  plants  because  i  1  >  it  was  extremely  difficult  to  observe  the 
fungous  threads  of  the  internal  mycorrhiza  grow  through  the  cell 
wall    of  the   rootlets   into  the  culture    medium    without,   and    (2)    be- 

rernetz,  Charlotte,  Ph.  I  >.  Assimilation  des  atmosphiirischeu  Stickstoffs 
<lmvh  einen  torfbewohnendea  I'ilz.  Berlchte  der  Deutschen  Botanischen 
Gesellschaft,  \"!.  '-'•-'.   L904,  pp.  267  274. 

^Ternetz,  Charlotte,  Ph.  1>.  Cleber  die  Assimilation  des  atmosphtlrischen 
Stlckstoffes  <lur.li  Pllze.  JahrbQcber  f"iir  Wissenschaftllche  Botanlk,  vol.  ii. 
L907,  pp    353    108. 

MTos       Hull,  la::     10         I 


50  EXPERIMENTS    IN    BLUEBERRY    CULTURE. 

cause  when  she  proposed  to  inoculate  nrrycorrhiza-free  seedlings  of 
the  host  plants  with  spores  from  the  pycnidia  that  formed  in  her 
cultures  she  was  unable  to  grow  any  seedlings  that  were  free  from 
mycorrhiza. 

Notwithstanding  the  lack  of  an  absolute  demonstration  that  the 
nitrogen-fixing  fungi  grown  by  Miss  Ternetz  were  identical  with 
the  ni\ 'corrhizal  fungi  of  their  hosts,  it  is  regarded  as  quite  possible 
that  the  mycorrhiza]  fungi  that  occur  in  perhaps  all  plants  of  the 
heather  and  blueberry  families,  including  the  swamp  blueberry,  are 
nitrogen  fixers,  and  thai  the  host  plants  absorb  this  nitrogen,  giving 
in  exchange,  for  the  use  of  the  fungus,  sugar  or  some  other  carbo- 
hydrate. 

The  experiments  thus  far  described  in  the  present  paper,  and  the 
accompanying  discussions,  appeal'  to  warrant  the  following  theory 
of  the  method  of  nutrition  of  the  swamp  blueberry: 

(a)  The  swamp  blueberry  grows  in  peaty  soil-  which  contain 
acid  or  other  substances  poisonous  to  plants. 

(b)  As  a  protection  against  the  absorption  of  amounts  of  these 
poisons  great  enough  to  prove  fatal,  this  plant,  like  many  other  bog 
and  acid-soil  plants,  is  devoid  of  root  hairs  and  consequently  has  a 
restricted  capacity  for  absorbing  soil  moisture.  This  low  absorptive 
capacity  is  correlated  with  a  low  rate  of  transpiration.  Many  bog 
shrubs,  although  living  with  an  abundant  supply  of  moisture  at  their 
roots,  have  been  recognized  as  showing  adaptations  for  retarded 
transpiration  similar  to  desert  plants. 

(c)  The  special  danger  to  which  the  swamp  blueberry  is  exposed 
by  reason  of  its  low  transpiration  and  its  corresponding  reduced 
capacity  for  absorption  is  insufficient  nutrition.  The  danger  of 
nitrogen  starvation  is  particularly  great  since  these  soils  contain  very 
little  nitrates. 

(d)  Some  bog  plants  similarly  threatened  with  insufficient  nutri- 
tion, such  as  the  sundew-  (  Drosera ).  the  bladderworts  (  Utricularia  ). 
and  the  pitcher  plants  (  Sarracenia  ) ,  possess  means  of  securing  the 
requisite  nitrogen  by  catching  insects  and  digesting  and  absorbing 
their  nutritive  pails. 

(e)  In  the  swamp  blueberry  the  required  nitrogen  is  secured  in 
a  dillerenl  way.  The  plant  associates  with  itself  a  mycorrhi/.al 
fungus  which  is  able  to  assimilate  nitrogen  from  the  surrounding 
organic  matter,  and  perhaps  from  the  atmosphere  also,  and  to  convey 
ii  into  the  plant  without  taking  along  with  it  a  large  amount  of 
I  he  poisonous  soil  moisture. 

Whether  this  theory  of  the  nutrition  of  the  swamp  blueberry  i-  or 
is  not  substantiated  in  all  its  details  by  future  investigation,  it  has 
afforded  a  useful  basis  for  cultural  experimentation,  as  will  be  evident 
from   the  results  about   to  be  described. 
103 


L'HK    RAIS1  Nil    i  'l      HI  I    I  HI  Kin     SKKDLI  NUS.  5  1 

A    METHOD   OF   POT   CULTURE. 

(20)     Si  I  lis     ill       llll      SWAM1'     i;i  I   I  i:i  kkv      SOWN     IN      \li.lsl      KKOM     1KIMI      III  ttltlKS 

;  m  i  \  \  ii    in    \i;nr  i    i  i\  i    \vi  i  lis. 

The  experiments  in  the  raising  of  bluebern  seedlings  have  covered 
such  a  great  diversity  of  soil  mixtures,  methods  of  potting,  manner 
of  watering,  amounl  of  shade,  and  day  and  night  temperatures  thai 
an  account  of  all  <>l'  them  i-  out  of  the  question.  The  mure  impor- 
tant results  of  these  experiments  may  be  presented,  however,  in  an 
accounl  of  the  seedlings  of  1908.  the  latest  thai  have  been  grown 
for  an  entire  year,  with  allusions  in  the  experiments  of  other  years 
whenever  additionally  useful.  The  parent  plant  of  the  seedlings  of 
1908  is  described  on  page  s<i. 

The  method  followed  in  germinating  the  seed  was  that  developed 
li\  Mr.  George  \V.  Oliver,  of  the  Bureau  of  Plant  Industry,  in  190*2. 
AM  other  experimenters,  apparently,  have  considered  ii  necessan 
to  keep  the  seeds  dormant  by  stratification  or  some  equivalent  mean 
until  late  winter  or  early  spring  and  then  to  give  them  the  warmth 
necessan  for  germination.  \U  Mr.  Oliver"*  method,  however,  the 
seetU  are  sown  in  August,  -non  a  tier  the  maturity  of  the  berries;  they 
begin  to  germinate  in  about  five  weeks,  and  by  proper  handling  in 
the  greenhouse  they  are  robust  plants  by  ihe  beginning  of  summer 
instead  of  i  in\  seedlings. 

Pursuing  this  method  the  detailed  operations  were  as  follows: 
The  berries  (PI.  VI.  fig.  1)  when  fully  matured  and  slightly  fer- 
mented were  mashed  to  a  pulp  and  rubbed  thoroughly  under  water. 
The  juice  and  floating  pulp  were  washed  away,  and  the  heavy  seeds, 
which  sank  tn  the  bottom,  were  taken  oul  and  their  superficial  mois- 
ture dried  nil  li\  exposure  to  the  air  for  a  few  hours.  When  thus 
prepared  and  placed  in  a  closed  bottle  blueberry  seeds  will  retain 
their  vitality  for  several  week-,  probably  for  several  months. 

I  mm  the  ■_'  quarts  of  berries  were  secured  12.5  grams  of  dry  seeds. 
The  seeds  numbered  aboul  9.000  per  gram,  of  which  about  three- 
fourths  were  small  and  contained  no  embryos.  Aboul  II  grams  were 
usee)  to  rai-e  seedlings,  computed  to  contain  aboul  25,000  germinable 
seeds.  Ii  furnished  an  abundant  amount  for  seeding  four  ordinary 
gardener's  flats,  and  from  these  over  1.000  seedlings  were  actually 
transplanted  and  as  many  more  might  easily   have  been  utilized. 

The  mature  seeds  (PI.  \"I.  figr,  o)  are  roughh  orbicular  ar- 
row h  oblong  in  outline,  strongly  flattened,  with  a  deeply  pitted  seed 
coat.      They   vary   in   length    from  0.0-1    to  O.Ofi  of  an   inch    (1   to   1.5 

nun.  |  . 

The  seeds  were  -own  in  -hallow   w [en  flats  10  l>\   M  by  •">  inches. 

inside  measurement.     After  crocks  |iad  been  placed  over  the  drain 
age  holes  the  bottom  was  covered  to  a  depth  of  about   an  inch  with 

193 


52  EXPERIMENTS    IN    BLUEBERRY    CULTURE. 

kalmia  peat  in  fibrous  form  to  insure  good  drainage.  Over  this  was 
placed  the  finely  sifted  soil  of  the  seed  bed.  trodden  down  with  the 
whole  weight  of  the  body,  the  total  thickness  of  the  soil  and  drain- 
age being  2.5  inches. 

The  soil  of  the  seed  bed  in  this  instance  was  a  mixture  of  the 
following,  each  rubbed  through  a  wire  sieve  with  ,',.,-ineh  square 
openings: 

Kalmia  peat  .  8  parts  by  bulk. 

Sand 2  parts  by  bulk. 

Live  sphagnum 2  parts  by  bulk. 

Loam 1  part  by  bulk. 

While  this  mixture  gave  good  results,  certain  modifications  in  the 
direction  of  simplicity  have  been  found  equally  satisfactory  so  far 
as  growth  is  concerned,  and  more  satisfactory  with  regard  to  the  ease 
of  transplanting.  These  changes  involve  the  omission  of  the  loam, 
which  from  other  experiments  is  now  regarded  as  never  advanta- 
geous and  sometimes  actually  injurious,  and  the  omission  of  the  sphag- 
num, which,  although  a  good  moisture-holding  and  aerating  me- 
dium, appears  to  be  superfluous  in  a  peat  and  sand  mixture.  The 
sphagnum  also  interferes  somewhat  with  the  clean  pricking  out  of 
the  seedlings  in  the  first  transplanting.  From  experience  with  vari- 
ous other  seedlings  of  blueberries  a  mixture  of  2  parts  of  finely 
sifted  kalmia  peat  to  1  part  of  sand  is  regarded  as  satisfactory  and 
preferable.  The  peat  should  be  well  rotted  and  the  sand  clean  and 
free  from  lime.     This  matter  is  more  fully  discussed  on  page  60. 

After  the  seed  bed  had  been  prepared,  as  already  described,  the  dry 
seeds  were  scattered  upon  it  and  covered  with  about  an  eighth  of  an 
inch  of  the  same  soil  lightly  sifted  over  it.  The  surface  was  then 
sprinkled  with  water  from  a  sprinkling  pot  provided  with  a  very 
tine  rose. 

So  far  as  moisture  is  concerned  the  ideal  condition  of  the  seed  bed 
is  that  the  soil  should  lie  just  damp  enough  so  that  it  shall  not  be- 
come dry  on  the  surface.  The  drying  of  this  peat  is  indicated  by  a 
conspicuous  color  change,  from  dark  brown  to  light  brown.  If  ex- 
posed directly  to  an  ordinary  greenhouse  atmosphere,  the  tendency 
of  the  seed-bed  surface  to  become  dry  will  necessitate  frequent  ap- 
plications of  water,  and  the  bed  will  be  in  danger  of  repeated  periods 
of  sogginess.  These  conditions  may  lie  very  much  improved  by  cov- 
ering the  ilat  with  panes  of  glass.  An  opening  about  an  inch  wide 
should  be  left  at  either  end  to  permit  the  circulation  of  air  over  the 
seed  bed.  This  ventilation  will  prevent  the  excessive  accumulation 
of  moisture  in  a  stagnant  atmosphere  and  will  also  prevent  over- 
heating on  sunny  days,  both  of  which  conditions  are  injurious  to 
seedlings.  A  flat  thus  covered  may  not  require  watering  for  inter- 
vals of  several  days.    The  advantages  of  the  glass  covering  are  par 

193 


Bui.  193.  By,  .    u.  S   Dopt.  of  Agi 


Plate  VI. 


9^  V 

* 

«£^/@ 

F       1.— Swamp  Blueberries  from  the  Parent  Bush  of  the  Seedlings  of  1908. 

ed  after  remaining  nearly  a  yi  nlin,  and  the  illustration 

not  show  ilu-ir  maximum  si/r  and  plumpness.     (Natural  size,  i 


Fig.  2.— Seeds  of  the  Swamp  Blueberry. 

nr-o'.l  In  di 


GERMINATION    I  >l     Bl  I   i  Bl  Rm     S]  I  DS. 


53 


Fig.  19.-  Section  of  ;i  blue 
berry  seed  :  </.  Embryo :  '/. 
endosperm  ;  c,  outer  seed 
coat,  i  Enlarged  1 8  diame- 
ters.) 


ticularly  evident  when  germination  begins,  for  manj  of  the  eed 
have  been  washed  to  the  surface  in  the  process  of  watering  and  have 
germinated  without  any  soil  covering.  It  ma\  be  several  days  before 
the  root  penetrates  the  soil,  but  the  moisture  maintained  in  the  air 
underneath  the  glass  keeps  these  naked  seedlings  from  death  by  dry 
ing.  After  germination  has  progressed  so  far  that  a  good  stand 
of  seedlings  is  assured  the  glass  should  be 
gradually  removed. 

The  flats  seeded  on  Vugust  12,  L908,  were 
kept  in  a  greenhouse  as  cool  as  practicable 
and  shaded  from  the  sunlight.  When 
started  in  winter,  -red  flats  should  be  kept 
at  a  temperature  not  less  than  50  to  60  V. 
at  night  and  about  15  degrees  higher  in  the 
daytime.  Under  such  conditions  sunlight 
during  the  whole  day  -rein-  to  benefit  them. 
Germination  began  on  September  !>. 
thirty-seven  days  after  seeding,  and  eon- 
tinned  for  more  than  two  months.  In  other  seedings  of  this  and  the 
closelj  related  I •  1 1 it  I lerries  known  as  Vaccinium  atrococcnm  and  V. 
pallidum,  germination  has  begun  in  as  short  a  period  as  twenty  five 
days.  This  slowness  of  germination  might  be  considered  merely  a 
feature  <>!'  the  genera]  sluggishness  of  growth  in  these  plant-.  It  is 
in  fact,  however,  due  to  a  much  more  specific  cause.  The  food  stored 
in  the  seed  for  the  nourishment  of  the  plantlet  is  not  located  in  the 

cotyledons,  as  in  the  bean  or  pea. 
for  example,  but  it  lies  in  a  mass 
called  the  endosperm,  quite  outside 
the  embryo,  t  Sec  fig.  L9. 1  It  re 
quires  several  week-  for  the  minute 
embrj  o,  feeding  on  t  he  large  mass 
of  surrounding  endosperm,  to  grow 
to  sufficient  size  to  burst  open  the 
seed  coats.  Until  the  embryo  has 
attained  such  size  it  is  physically 
impossible  for  the  -eed  to  ger- 
minate. 

When  the  seedlings  had  straightened  themselves  out  they  were 
about  0/2  to  0.3  of  an  inch  (5  to  8  mm.)  high  and  the  newly  expanded 
cotyledons  about  0.0G  of  an  inch  (1.5  mm.)  long.  (See  fig.  20.) 
Wit  Inn  a  few  day-  the  first  foliage  leaf  began  to  appear  between  the 
cotyledons  about  0.06  of  an  inch  (1.5  mm.)  long.  (See  fig.  20.) 
inch  i  Hi  to  15  nun.  i  high,  the  erect  unbranched  stem  bearing  four 
or  five  foliage  leave-,  and  the  cotyledons  having  expanded  to  a  length 
of  0. 12  of  an  inch  (3  mm.  >.  i  See  fig.  21.) 
ia:i 


Kn;.  20. —  Blueberry  seedlings  In  th<   ■ 
ledon  stage    a,  Befoi  el  ion  of 

b,  :n   the  beginning  of 
the    development    of    the    flrsl    foliage 
'  Enlarged  2  diameters,  i 


54  EXPERIMENTS    IN     BLUEBERRY    CULTURE. 

Although  the  leaves  of  the  parent  plant  had  entire  margins,  the 
leaves  of  the  young  seedlings  were  invariably  serrulate.  It  was  only 
after  the  plants  were  several  months  old  that  any  of  the  branches 
began  to  produce  leaves  with  entire  margins,  and  some  of  the  seedlings 
from  this  parent  give  promise  of  permanently  retaining  the  serrulate 
lea  l'  character.      (  See  p.  82.) 

(21)  The  seedlings  are  first  transplanted  at  the  agi   <>i    aboot   six  weeks, 
when  they  are  approaching  an  inch  in  height. 

On  October  24  the  first  transplanting  was  done  from  the  mh^\  flats 
of  1908.  A  new  flat  was  filled  to  a  depth  of  '2  inches,  trodden  down 
hard,  with  the  following  mixture: 

K .- 1 1 1 1 1 i : i     peat,    rutted    for    several     months    and 

rubbed  through  a  quarter-inch  sieve 8  parts  by  bulk. 

Sand,   coarse,    washed lpartbybulk. 

Loam,  clayey,  finely  sifted lpartbybulk. 

This  soil  mixture  was  used  as  the  result  of  experience  of  the  two 
preceding  years.     From  a   few  experiments  made  in  the  winter  of 

L906— 7  it  had  been  found  that  a  mixture  of 
equal  parts,  by  bulk,  of  peat,  sand,  and 
loam  was  decidedly  superior  to  loam  and 
manure  or  to  sand,  sphagnum,  and  loam. 
In  the  winter  of  11)07-8  it  was  found  that 
the  amount  of  sand  and  loam  could  be  re- 
duced with  distinct  advantage,  and  as  a 
result  of  the  experiments  then  made  many 
of  the  cultures  of  1908-9  were  grown  in 
the  mixture  described  above  (peat  8,  sand 
1.  loam  1).  The  retention  of  the  loam  was 
due  to  an  idea  that  this  ingredient  would 
furnish  some  necessary  mineral  nutrient 
not  furnished  by  the  peat.  From  an  ex- 
periment made  in  the  summer  of  1909. 
however  (p.  69),  ii   was  found  that  under 

the  System  of  handling  the  pots  described 
Fig.     21.—  Blueberry    seedling  ._   .  ,  ,   . 

i ni  six  weeks  old.  with  five     <»'   page  •>,    large  plants  repotted   in  a   peat 

foliage  leaves.     (Enlarged  2      S(!j]    with    no    loam    whatever   made  a    better 
diameters.  >  ,1^1  1    ■ 

growth  than  those  potted  in  a  peat  con- 
taining a  tenth  part  of  loam.  There  is  some  reason,  therefore,  to 
suspect  that  loam,  even  in  such  a  small  quantity,  may  be  slightly 
injurious,  and  more  reason  to  suspect  that  it  may  be  superfluous. 
Experiments  intended  to  throw  light  on  this  question  arc  now  in 
progress. 

In  the  soil  of  the  Hat.  prepared  as  described  above,  80  plants  were 
set    "_;    inches  apart.     They   were   pricked   out   of  the  seed   bed   and   set 
193 


Till.  \  I  \l  i  \  i    OF    THE    i'OUNG    SEEDLINGS.  .'.."> 

in  the  new  soil  l>\  means  of  a  -mall  dibble.  These  plants  were  halt' 
to  three- fourths  of  an  inch  high  and  had  three  to  six  true  leaves. 

It  i-  believed  that  a  spacing  of  2.5  inches  in  the  flat  is  better  than 
■_'  inches,  as  the  plants  have  a  little  more  room  and  the  2.5-inch  square 
of  earth  is  a  very  convenient  size  when  the  next  transfer  is  made 
into  I  inch  pots. 

From  this  time  on  during  the  winter  the  plain-  were  kept  in  a  cool 
greenhouse  in  which  the  night  temperature  was  •">•">  to  t'>o  F..  and 
which  was  given  a  large  amount  of  ventilation.  The  day  tempera- 
ture reached  ordinarily  65  to  TO  F.  It  was  found  that  a  house 
with  a  nighl  temperature  of  l<>  I*",  and  a  day  temperature  of  60  F 
was  too  cold  for  such  seedlings,  as  they  made  almost  no  growth  at 
all.  In  a  warm  house,  65  to  70  at  night  and  80  to  90  F.  in  the 
daytime,  blueberries  grow  fairly  well,  but  they  are  much  subject  to 
injury  by  red  spider  (Tetranychus  bimaculatus) ,  and  their  new 
growth  while  sufficiently  extensive  does  not  appear  so  robust  as  in  the 
60    to  To    F.  house. 

For  the  first  few  days  the  newly  transplanted  seedlings  were  shel 
tered  from  direct  sunlight.  Later,  however,  they  were  given  all  the 
sunlight  possible.  It  was  found  that  during  the  winter,  when  well 
established  in  a  suitable  soil  and  under  proper  moisture  conditions, 
the  plant-  greys  better  when  they  received  the  fullest  sunlight  that 
the  greenhouse  afforded.  This  statement  applies  t<>  the  plants  in  all 
stages,  whether  in  a  seed  bed  or  alter  the  first  transplanting  or  in 
larger  puts. 

In  watering,  the  plants  should  be  kept  "on  the  dry  side,"  as  gar 
doners  say.  Water  may  advantageously  be  withheld  until  the  surface 
of  the  -oil  is  dry.  hut  this  condition  should  not  be  allowed  to  extend 
lo  a  depth  id'  more  than  aboul  an  eighth  of  an  inch.  Then  a  rather 
thorough  watering  should  be  given,  which  will  carry  moisture  to  the 
bottom  <d  the  -oil.  but  not  run  through.  Such  a  watering  at  infre- 
quent intervals  is  preferable  to  frequent  light  sprinklings  thai  moi  ten 
the  surface  only.  Except  for  the  brief  period  of  percolation  imme 
diatels  after  watering,  the  movement  of  water  in  the  soil  should  be  a 
capillary  one,  and  from  the  bottom  upward.  Under  such  conditions. 
if  the  -oil  i-  of  proper  texture,  good  aeration  i-  insured. 

The  -hock  of  transplanting  check-  the  growth  of  the  - llings  for 

several  days.  Tin-  checking  of  growth  may  manifest  it-elf  in  one  or 
more  of  three  ways:  ( it )  The  withering  of  the  stem  tip:  ( /> )  the 
"stagnation,"  or  stoppage  of  expansion  of  the  uppermost  leaf  rudi- 
ment :  and  i  i  i  the  purpling  of  the  older  lease-.  A-  these  phenomena 
when  persistent  have  been  much  utilized  in  these  experiment-  as 
warnings  of  the  existence  of  condition-  antagonistic  to  growth  and 
a-  they  may  he  of  similar  assistance  to  other  experimenters,  a  de- 
scription  of  them  will  he  given. 

193 


56  EXPERIMENTS    IN    BLUEBERRY    CULTURE. 

The  withering  of  the  tip  includes  the  uppermost  leaf  rudiment  and 
the  growing  point  of  the  stem  inclosed  within  its  folded  base.  The 
tissues  turn  brown  and  become  dry,  and  the  growth  of  that  axis  is 
terminated.  The  resumption  of  growth  from  such  a  stem,  if  it 
occurs,  takes  place  through  the  formation  and  expansion  of  a  bud  in 
the  axil  of  the  leaf  next  below  the  withered  one.  This  withering  of 
the  tip  is  readily  distinguishable  by  its  color  from  a  partial  blacken- 
ing of  the  uppermost  tender  leaves  which  sometimes  occurs,  appar- 
ently a  pathological  disturbance  of  a  temporary  character  and  usually 
not  affecting  the  growing  point  of  the  stem  itself.  The  brown  wither- 
ing of  the  tip  seldom  takes  place  when  the  leaf  rudiment  involved  in 
the  withering  is  more  than  0.1  inch  (2.5  mm.)  in  length.  When  longer 
than  that  it  usually  keeps  on  expanding.  This  withering  of  the  tip- 
has  been  almost  wholly  prevented  when  the  shock  of  transplanting 
was  rendered  as  light  as  possible  by  suitable  precautions,  including 
(a)  a  soil  in  perfect  condition  for  the  nutrition  of  the  plants,  espe- 
cially that  in  which  the  peat  is  well  rotted  (p.  CI)  ;  (b)  the  transfer 
of  the  plants  to  their  new  bed  without  injury,  especially  without 
destroying  any  part  of  the  roots;  («?)  the  shading  of  the  plants 
from  direct  sunlight  for  two  weeks  or  more,  until  their  new  root 
growth  is  well  established,  and  their  subsequent  gradual  adjustment 
to  full  sunlight;  and  (d)  the  holding  of  the  transplanted  plants  in 
a  warmer,  moister  atmosphere,  about  65c  at  night  and  80°  F.  in 
the  daytime.  Whether  or  not  this  last  condition  had  a  real  influence 
on  the  prevention  of  the  tip  withering  is  not  definitely  known. 

The  stagnation  of  the  uppermost  leaf  rudiment  does  not  attract  the 
inexperienced  observer's  attention  so  readily  as  its  withering.  With 
a  little  experience,  however,  it  is  easily  detected.  Ordinarily  the 
leaves  of  a  growing  stem  follow  each  other  at  a  rather  dose  interval, 
so  that  by  the  time  a  half-grown  leal'  is  ready  to  flatten  out.  from  its 
boat-shaped  folding  in  the  younger  stage,  the  succeeding  leaf  is  com- 
monly a  third  or  more  the  length  of  the  one  that  is  flattening  (fig. 
22).  When  stagnation  occurs,  however,  the  uppermost  leaf  rudiment 
promptly  stops  growing,  usually  at  a  length  of  0.04  inch  (1  mm.)  or 
less,  while  the  young  leaf  next  below  it  goes  on  flattening  and  glow- 
ing to  nearly  its  normal  size.  The  end  of  the  stem,  therefore, shows  a 
nearly  full-grown  flat  leaf  with  a  minute  leaf  rudiment  at  its  base 
seldom  more  than  a  fifth  and  often  not  more  than  a  tenth  its  own 
length. 

The  purpling  of  leaves,  to  which  allusion  has  been  made,  does  not 
refer  to  the  reddish  translucent  appearance  of  the  growing  twig  tips. 
That  i-  the  normal  coloration  in  the  blueberry,  as  it  i-.  for  example, 
in  the  rose.  The  purpling  now  under  consideration  occurs  in  the 
mature  leaves,  which  are  normally  green,  and  is  of  a  dark  shade.  It 
is  commonly  accompanied   by  a  conspicuous  reddening  of  the  leaf 

[93 


PREVENTION    OF    INJUR!     IN    TRANSPLANTING. 


57 


veins.    This  purpling  of  the  old  leaves  is  evidence  of  a  severe  stop 
of  growth  and   in  these  experiment?   has  been  observed  to  I" 
caused  by   lov    temperature,  about    In     F.  or  lower,  or  by  hick  of 
nutrition  from  any  cause,  or,  apparently,  by  poisoning. 

[f  the  soil  into  which  young  blueberry  seedlings  arc  transplanted 
is  suited  to  their  growth,  purpling  of  the  old  leaves  seldom  occurs, 
the  e\  idence  of  the  -hock  of  transplanting  being  confined  to  the  po- 
sible  withering  of  a  few  of  the  stem  tips  and  the  temporary  stagna- 
tion of  other-.     In  -nine  transplantings  no  withering  of  tips  occur-. 

During  the  period  of  cessation  of  stem  growth  after  transplanting, 
the  plant  is  by  no  mean-  idle,  for  the  roots,  as  shown  in  glass-pot 
cultures,  continue  to  make  new  growth,  and  when  this  has  sufficiently 
progressed  stem  growth  is  resumed. 

(22)     Will  N      IBOl    l      UN     WEEKS    OLD     \M>    NEARLY    TWO    INCHES     in     HEIGHT    THE 
SEEDLINGS  BEGIN    TO  SEND  OU1    BASAL  BRANI  HES. 

An  important  phase  in  the  development  of  the  seedlings  of  1908 
began  on  November  25,  when  one  of  the  plant-  commenced  to 
out  a  branch  from  the  axil  of  a  cotyledon. 
At  the  expiration  of  another  month  75  per 
cent  of  the  plants  in  the  flat  had  put  out 
similar  basal  branches,  and  the  remaining 
25  per  cent  ultimately  did  the  same. 

These  basal  shoots  are  of  the  highest  im- 
portance in  the  economy  of  the  blueberry 
plant,  for  they  soon  far  out-trip  the  lir-t 
stem  and  become  the  principal  seat  of 
growth,  until  they  themselves  are  over 
shadowed  by  later  and  -till  more  vigorous? 
basal  shoots.  The  original  stem  of  the  seed- 
ling never  develops  into  an  ultimate  main 
stem  or  trunk,  but,  as  will  be  seen  later 
(p.   58),  stops  growing  while  the  plant   is 

-till  young,  and  afterward  dies.     It  is  this  habit  of  sending  up  basal 
shoots  thai  makes  the  swamp  blueberry  a  many-stemmed  bush,  nol  a 

miniature  tree  \\  ith  a   single  trunk. 

The  development  of  basal  shoots  began  when  the  seedlings  had 
about  12  leaves  and  were  about  L.5  to  2  inches  high.  In  this  lir-t 
basal  branching  the  number  of  branches  varied  from  1  to  3.  Out  of 
73  plant-  on  which  the  branching  was  recorded  39  had  1  branch,  30 
had  ■_'  branches,  and  I  had  3  branches.  The  branches  occurred  in 
the  axils  of  the  cotyledon-  or  of  one  of  the  lir-t  four  lca\  es.  Of  the 
39  plain-  with  1  branch,  1 1  had  the  branch  in  the  axil  of  a  cotyledon. 
17  in  the  axil  of  the  first  leaf,  8  the  second,  2  the  third,  and  1  the 
fourth.    Of  the  30  plant-  with  2  branches,  II  had  both  branch 

193 


I'm.   22.     Normal  t  i|>  ol 
in    a    blueberry     seei 
a  rged      I     dlatu 
the  smaller  figure  natural 


58 


EXPERIMENTS    IN    BLUEBERRY    CULTURE. 


the  axils  of  the  cotyledons,  13  had  neither  branch  so  situated,  and  6 
had  1  branch  from  a  cotyledon  axil  and  1  from  a  leaf  axil.  Of 
the  4  plants  with  3  branches.  3  had  all  3  branches  in  the  axil>  of  the 
cotyledons  and  the  first  leaf.  1  had  a  branch  in  the  axil  of  a  cotyledon 
and  of  the  first  and  second  leaf.  Of  the  total  111  branches  46  were 
in  the  axil  of  one  of  the  two- cotyledons,  an  average  of  •_':'>  to  each,  'M> 
in  the  axil  of  the  first  leaf,  20  the  second,  7  the  third,  and  2  the 
fourth.  In  the  order  of  the  frequency  of  production  of  a  basal  shoot. 
therefore,  the  first  leaf  stands  Hist,  a  cotyledon  next,  then  the  second, 
third,  and  fourth  leaves,  in  order. 

While  the  exact  location  of  the  basal  branches  appears  to  have  no 
special  significance,  the  number  of  the  branches  does,  for  the  habit  of 
producing  two  or  more  branches  i>  a  persistent  one  and  such  seedling> 
tend  to  produce  diffuse  plants  with  many  and  small  stems  and  small 
stature,  while  the  plants  with  the  single-branch  tendency  are  taller 
and  have  fewer  and  more,  robust  stems.  The  differences  in  general 
appearance  caused  by  the  two  types  of  branching  are  well  illustrated 
in  figures  24  and  25,  from  photographs  of  two  seedlings  of  11)07  made 
at  the  age  of  10  months. 

(23)   When   the   seedlings    are   about    four   months   old   and   about   threk 
inches  in  height  the  growth  of  the  original  stem  terminates. 

On  January  5, 1909,  the  growing  tip  on  the  original  stem  of  one  of  the 
plants  withered.  At  that  time  this  stem  was  about  2.5  inches  high,  had 
14  leaves,  and  had  2  vigorous  basal  shoots  about 
an  inch  in  length.  This  withering  differed  in 
one  important  respect  from  the  withering  due 
to  shock,  described  on  page  50.  In  that  case  it 
was  an  ordinary  leaf  rudiment  that  withered. 
In  the  present  case  the  withering  was  fore- 
shadowed by  the  development  of  a  minute  brad 
( lie;.  23).  This  differed  from  the  ordinary  leaf 
rudiment  in  the  absence  of  the  glandular  hairs 
characteristic  of  young  leaves,  and  it  remained 
small  until  the  leaf  next  below  it  had  become 
more  than  ten  time-  as  long.  Then  the  bract 
withered  and  the  growth  of  the  original  stem 
was    permanently    terminated.     The    same    de 

larged  4  diameters •  the     velopment    went    on    in    the   other    plants    until 
smaller    figure    natural      ;|(    (|u,        (j   ()f  .,   nH)lllh   ,;;,   per  ,.,.„,    .,11(1    j„   two 

months  '.).'>  per  cent  of  the  plants  had  terminated 
the  growth  of  their  original  stems. 

In  the  individual  plant  the  termination  of  growth  on  the  original 
Stem  took  place  after  the  basal  shoot  or  shoots  had  reached  a  stage  of 
193 


Fig.  23. — Bract  ami  young 
leaf  al  (lie  end  of  the 
original  stem  in  a  blue- 
berry     seedling.     <  En 


BRANCHING    OF    THE    SEEDLINGS. 


59 


\  igorous  development.  Out  of  fifty-nine  normal  cases  observed  prior 
Lo  the  second  transplanting  of  the  seedlings,  the  Length  of  the  new 
shoot,  or  when  more  than  one  the  longest  of  them,  at  the  time  of 
termination  of  growth  on  the  old  stem  varied  from  0.4  of  an  inch  to 
5  inches,  with  an  average  of  L.8  inches.     It  would  appear  that  the 


Fig     -i       Blneberrs    --i'iIUhlc    with    diffuse  i-'u;.    25.      Blueberry    seedling    of    the  type 

i.\i (   branching.     This   will    become  a  with  few  branches      The  branch  is  more 

low,     many-branched     bush        (One-third  than   twice  as   tail   as   the  original  main 

natural  sizo.i  stem.     (One-third  natural  size. ) 


immediate  cause  of  the  termination  of  growth  on  the  old  stem  is  the 
diversion  of  food  materials  into  the  new  vigorous  growth. 

(  'J  I  i    Will  \     I  III     PLANTS    \i:i      Willi    I    1  l\  I     MONTHS  OLD  AND  FOVR  TO  SIX    INCHES    IN 
Ml  l(. II  I      I  III  -i      Mil      POTTED    IIS     FOUR-INCH     POTS     in      IES1     PEAT    OR    PEAT 

MlVllltl  . 

( )n  February  17.  when  the  plants  were  I  to  6  inches  high,  they  were 
transplanted  into  1  inch  pots  in  the  -nine  -oil  mixture  a-  was  used  in 
the  transplanting  of  October  24   (peal  8,  sand  L,  loam  I).     A.s  stated 

19."! 


60  EXPERIMENTS    IN    BLUEBERRY    CULTURE. 

in  the  discussion  of  that  transplanting,  the  plant-  would  probably 
have  done  somewhat  better  without  the  loam.  In  addition  to  the 
crock  over  the  drainage  hole,  a  mass  of  fibrous  kalmia  peat  was  placed 
in  the  bottom  of  the  pot,  filling  it.  when  pressed  down,  to  the  depth 
of  an  inch  or  more.  After  cutting  the  soil  in  the  flats  into  rectangular 
cakes,  the  plants  were  lifted  and  transferred  to  the  pots  with  the  least 
possible  disturbance  of  the  roots. 

Several  experiments  had  been  made  earlier  to  ascertain  whether 
at  the  first  transplanting  from  the  seed  bed  it  is  better  to  set  the 
plants  in  flats  or  to  put  them  in  2-inch  pots,  or  thumb  pots  as  they 
are  more  commonly  called.  It  was  found  that  when  the  plant-  in 
thumb  pots  were  set  on  a  greenhouse  bench  they  tended  to  dry  out 
so  rapidly  that  it  was  impracticable  to  keep  them  in  the  right  con 
dit ion  of  moisture.  They  became  so  frequently  too  wet  or  too  dry 
that  their  growth  was  interrupted  and  they  were  much  inferior 
to  the  plants  in  the  flat--.  Other  plants  in  thumb  pots  (PL  VII). 
plunged  in  either  sand,  peat,  or  sphagnum,  made  about  the  same 
growth  as  the  plants  in  the  flats,  but  showed  no  uniform  advantage 
over  them,  either  while  they  were  in  the  thumb  pots  or  after  a 
second  transplanting.  The  labor  of  transplanting  and  of  maintain- 
ing uniform  moisture  is  somewhat  greater  in  the  case  id'  the  potted 
plants.  All  things  considered,  in  the  original  transplanting  the 
use  of  flats  is  regarded  a-  preferable  to  2-inch  pots. 

It  is  desirable  to  consider  at  this  time  the  exact  qualities  of  the 
soils  used  in  the  potting  mixtures.  As  already  stated,  it  is  regarded 
a-  preferable  to  omit  the  loam. 

The  sand  should  be  free  from  lime,  as  most  -and  is.  in  fact.  Ii 
should  also  be  as  clean  as  possible.  If  the  only  sand  obtainable  is 
mixed  with  clay,  this  should  he  removed  by  repeated  washing  in 
water. 

The  condition  of  the  peal  should  also  be  carefully  considered,  as 
shown  by  the  following  experience  during  the  progress  of  these 
experiments.  From  the  seedlings  of  L908  many  series  of  trans- 
plantings  were  made  on  various  day-  in  October.  November,  and 
December.  In  the  latter  part  of  December  it  was  noticed  that  while 
in  some  of  the  transplantings  the  seedlings  were  growing  vigorously, 
other  cultures  were  not  doing  well  at  all.  Many  of  the  tip-  were 
withered,  over  •_'.'>  per  cent  in  some  of  the  culture-:  the  rest  became 
stagnated  and  dark  purple,  and  remained  so  for  nearly  two  month-. 
All  possible  causes  of  the  trouble  having  been  eliminated  except 
those  due  to  (he  -oil.  the  characteristics  of  the  various  soil-  used 
were  considered  with  care.  At  this  time  the  writer  was  possessed 
of  the  erroneous  idea  that  lime  in  the  minutest  quantities  was  very 
injurious  to  the  blueberry  (p.  20),  and  consequently  it  was  sus- 
19:j 


Bui.  193.  Bureau  of  Plant  Industry,  U.  S.  Dept.  of  Agriculture. 


Plate  VII. 


a    o 
Bf    > 

1     X 


-.      O 

i     z 


'     O 


I  At  I  SSIVI     M  M'l  n    "i     fRESH    PEA  I  .  61 

pected  1 1 1 : 1 1  ilif  sand  was  impure  and  contained  lime.  An  exami- 
nation of  the  sources  of  the  different  kinds  of  sand  used  showed 
that  lime  could  no!  have  caused  the  trouble.  Finally,  however,  the 
various  cultures  were  arranged  by  the  dates  of  potting,  and  it  was 
then  found  thai  the  purpled  plants  had  all  been  potted  after  a 
certain  date,  on  which  a  new  lot  of  peat  had  been  received  at  the 
greenhouses.  The  peat  in  the  earlier  cultures  had  been  received 
in  June  and  at  the  time  of  the  first  transplantings  had  been  rotting 
for  four  months  at  a  warm  summer  temperature.  T1h>  seedlings 
transplanted  into  this  peat  did  uot  lose  their  tip-,  and  growth  was 
resumed  almost  immediately.  The  peat  used  after  the  middle  of 
Nbvembei  was  freshly  gathered,  and  it  was  in  this  fresh  neat  that 
the  seedlings  suffered  as  already  described.  It  should  be  stated 
here,  however,  that  by  the  end  of  two  months  these  seedlings,  which 
meanwhile  had  been  making  good  root  growth,  began  to  make 
rapid  top  growth  also  and  later  overtook  their  competitors. 

Acidity  tests  of  peat  from  the  various  cultures  and  in  different 
-  of  decomposition  showed  a  remarkable  correlation  between  the. 
acidity  of  the  peat  and  the  behavior  of  the  seedlings.  In  the  fresh 
deleterious  peat  the  acidity  was  excessive,  varying  from  0.03  to  0.046 
normal.  In  the  older  peal  in  which  the  plants  grew  well  the  acidity 
was  usually  not  in  excess  of  0.02  normal,  in  one  case  0.024.  Fresh 
peat  rubbed  through  a  quarter-inch  sieve  and  showing  an  acidity  of 
0.034  norma]  had  lessened  it-  acidity  to  0.02  normal  after  remaining 
in  a  moist  well-aerated  condition  for  three  weeks  in  the  warm  air  of 
a  greenhouse.  In  view  of  these  fact-  the  conclusion  was  reached  that 
the  deleterious  effect  of  fresh  peat  is  due  to  its  excessive  acidity. 

In  the  undisturbed  peat  of  a  kalmia  thicket  wild  blueberry  plants 
are  often  found  growing  luxuriantly.  After  this  peat  is  stripped 
from  the  ground  it  becomes  injurious,  as  has  been  shown,  to  blue- 
berry plants  that  are  potted  in  it,  this  injurious  quality  being  cor- 
related with  an  excessive  acidity.  The  question  arises,  What  ci 
this  increase  in  acidity  and  in  what  particular  part  of  the  soil  does 
it  reside?  It  was  at  first  suspected  that  the  excessive  acidity  was 
located  in  the  less  decomposed  upper  layers  of  leaves  which  the  roots 
of  the  blueberry  plants  in  a  wild  state  do  not  reach,  but  which,  when 
the  peat  is  rubbed  through  a  sieve,  go  into  the  resulting  mixture.  The 
leaf  layers  to  which  reference  is  here  made  are  not  the  uppermost, 
neail\  dry  layers  a  year  or  less  old,  for  these  are  removed  in  gather- 
ing the  peat .  la  it  the  part  iall\  rotted  layers  one  t"  two  years  old,  such 

a-  those  shown  in  Plate  IV.    An  examinati f  such  material  showed 

that  it   was  not  excessively  acid,  but  came  well  within  the  range  of 
acidity  beneficial  to  blueberry  plant-. 

An  acidity  determination   was  then   made  of  the  root-  in  the  peat. 

These  are  the  roots,  chiefly  of  oak  and  kalmia.  that   interlace  the 

193 


62  EXPERIMENTS    IX    BLUEBERRY    CULTURE. 

partly  decomposed  portions  of  the  peat  into  mats  or  turfs.  Their 
appearance  in  the  upper  part  of  those  turfs  is  shown  in  Plate  Y. 
figure  2.  Taking  some  of  these  turfs,  freshly  gathered,  the  soil  was 
all  shaken  from  them,  leaving  only  the  "  fiber,"  consisting  entirely  of 
these  fine  live  roots.  This  fiber  was  allowed  to  rot  for  a  few  days, 
and  an  acidity  test  was  then  made.  It  proved  to  be  0.07  normal,  an 
acidity  far  in  excess  of  that  which  had.  proved  injurious  to  the  blue- 
berry seedlings.  The  excessive  temporary  acidity  of  freshly  gathered 
kalmia-peat  turf  and  its  consequent  temporary  injuriousness  to  blue 
berry  plants  are  therefore  attributed  to  the  diffusion  through  the 
peat  of  the  acids  originating  in  the  roots  killed  in  the  process  of 
gathering  tin-  turfs. 

It  should  he  added  here  that  the  acidity  of  the  uppermost  layer 
of  undecomposed  leaves  a  year  or  less  old  is  very  great,  and  that 
care  should  consequently  he  exercised  to  keep  these  out  of  the  soil 
used.  A  test  of  dry.  brown,  newly  fallen  sugar-maple  leaves  showed 
an  acidity  of  0.i22  normal,  and  a  mixture  of  the  leaves  of  various 
species  of  oak  in  a  similar  condition.  0.4.  Incidentally,  attention 
may  he  called  to  the  presumable  efficiency  of  a  mulch  of  such  leaves 
in  maintaining,  by  mean--  of  its  leachings,  under  the  influence  of  the; 
natural  rainfall,  the  acidity  of  the  underlying  more  fully  decom- 
posed layers,  which  without  the  addition  of  fresh  organic  matter 
would  ultimately  become  alkaline.  (See  the  account  of  an  alkaline 
oak-leaf  mold  on  p.  35. ) 

(25)  Blueberry  plants  potted  ln  peat  may  bi  made  to  grow  mori  bapidl^  if 
they  auk  watered  oc<  vsionali.y  during  the  growing  si  \s<>\  with 
water  from   a   manure  pit. 

In  the  winter  of  1907-8  pottings  of  seedling  blueberries  from  seeds 
sown  in  August,  1S>07.  were  grown  in  various  greenhouses  of  the 
Department.  The  most  successful  of  these  pottings  consisted  of  89 
plants  in  a  mixture  of  peat,  sand,  and  loam  in  3-inch  pots.  Two  of 
these  plants  are  illustrated  in  figures  24  and  25.  It  had  been  sup- 
posed that  the  superior  growth  of  these  plants  was  the  result  of 
specially  favorable  conditions  of  light,  temperature,  and  watering, as 
indeed  it  was  in  part;  hut  in  the  following  winter,  during  an  inquiry 
about  certain  details  of  the  handling  of  (his  culture,  the  gardener 
in  charge  of  the  greenhouse  in  which  the  plants  were  grown  admitted 
that  during  a  portion  of  the  spring,  without  consultation,  he  had 
given  the  pots  an  occasional  watering  with  manure  water.  A.S 
manure  when  used  with  loam  in  the  winter  of  1906-7  had  proved 
positively  injurious  to  blueberry  plants,  its  possible  beneficial  effeci 
when  used  in  conjunction  with  peat  seemed  worth  testing  further. 
In  the  spring  of  1!)0!).  therefore,  various  cultures  were  watered  with 
manure  water  once  a  week,  the  amount  applied  being  the  same  as 
that  given  in  an  ordinary  watering  with  tap  water,  about  "><>  c.  c.  for 

193 


\l  \  \  l    l;l  .  ()3 

each  t-inch  pot.  The  application  was  made  to  -i\  cultures,  contain- 
ing altogether  156  plant-,  exactly  comparable  with  a  similar  number 
of  plant-  receiving  no  manure  water.  'The  applications  wort?  made 
in  April  and  Ma\  and  varied  in  number  from  five  to  eight. 

In  all  six  cultures  the  plant-  to  which  manure  water  had  been 
applied  made  a  more  vigorous  growth,  temporarily  at  least,  than 
those  that    received   none. 

Similar  results  were  secured  by  the  use  of  one-tenth  cow  manure, 
t're-hh  i-otied.  in  the  peat  mixture  in  w  hich  the  plants  were  potted. 

It  was  after  the  beneficial  effecl  of  this  manuring  had  begun  to 
-how  itself  that  a  statement  of  similar  results  nearly  a  century  old, 
in  the  culture  of  heath-,  came  to  the  writer'-  attention.  It  is  con- 
tained in  a  hook  l>\  William  McNab  entitled  "A  Treatise  on  the 
Propagation,  Cultivation,  and  General  Treatment  of  ('ape  Heaths," 
published  in  1832.  The  original  i-  now  rare,  bul  a  reprint  was  pub- 
lished in  1908  in  Note-  from  the  Royal  Botanic  Garden,  Edinburgh, 
volume  ■">.  pages  351  to  374.  McNab,  who  was  the  superintendent 
of  the  Edinburgh  garden  from  1810  to  L848,  was  undoubtedly  the 
most  intelligently  successful  grower  of  Cape  heath-  at  the  period 
of  their  greatest  popularity.  Hi-  treatise  is  original  and  practical 
and  delightfully  written  With  reference  to  the  manuring  of  heaths 
he  states  : 

l  may  mention  that   l  have  used  a  small  quantity  of  manure  in  the  foregoing 

compost  wiih  very  g l  effect,  aboul  one-eighth  pan  of  cow  dung.     This  should 

l>e  well  potted  before  it  is  used,  'the  way  thai  I  have  always  prepared  this 
dung  before  using  it  is  to  lake  a  barrow  lead  of  ii  and  place  il  in  thin  layers 
between  layers  of  peat  earth,  and  after  it  lias  lain  for  seme  time,  chop  the 
whole  en  together,  and  turn  ii  oxer  at  intervals  till  the  dung  disappears  and 
the  whole  mass  assumes  the  appearance  of  black  peat  earth  and  sand;  and 
where  this  manure  is  applied  aboul  an  equal  quantity  of  sand  should  be  added 
(thai  is.  aboul  one-eighth  part  >>f  the  whole)  ii.  addition  to  the  sand  that  I 
have  before  recommended  to  he  mixed  up  with  the  earth.  This,  I  know,  can  be 
used  with  very  good  effect,  but  for  all  ordinary  purposes  1  consider  it  quite 
unnecessary,  as  there  is  no  difficulty  in  growing  heaths  very  soon  too  large  for 
tlie  accommodation  that  is  generally  allotted  for  them,  with  the  compost  that 
I  have  mentioned  without  manure.  I  merely  mention  this  because  I  know  it 
is   the   opinion   of   some    that    heaths   will    not    thrive    wilh    manure   added    to   the 

peat  earth  in  which  they  are  grown. 

I  know,  however,  ihat  some  heaths  may  be  grown  to  a  larger  size,  in  the  same 

space  of  time,  witli  manure  than  without  it:  tint,  as  I  have  already  mentioned. 
I  consider  it  quite  unnecessary  for  all  ordinary  purposes,  and  any  person  who 
wishes  to  tt\  its  effects  should  do  -o  very  sparingly  at  lirsl.  till  he  is  enabled 
to   judge   Of    the   effecl    produced    by    It,    as   a    little   excess   of   manure    is    sure   In 

injure  the  plants.     Perhaps  liquid  manure  might  be  used  with  very  ur 1  effect 

for  growing  some  kinds  of  heaths,  hut  I  am  unable  to  give  any  particular  direc- 
tions in  what  proportion  it  should  he  used.  as.  from  wiiat  trials  I  have  made.  1 
can  not  come  to  any  certain  conclusion  But  this  much  I  know,  that  whoever 
wishes  to  try  it  should  do  so  at  titst  wiih  great  caution,  witli  quite  as  much  as 
in  using  an  excess  of  manure  in  its  solid  state. 
103 


64 


EXPERIMENTS    IN    BLUEBERRY    CULTURE. 


McNab's  conclusion  that  manure,  while  beneficial  in  small  quan- 
tities, should  be  used  with  caution  or  not  at  all  agrees  with  the 
conclusion  reached  from  these  blueberry  experiments.  On  page  18 
of  this  paper  is  described  the  disastrous  results  of  the  heavy  manur 
ing  of  blueberry  plants,  and  in  view  of  the  fact  that  the  blueberry 
makes  satisfactory  growth  without  manure  and  that  we  are  not 
sufficiently  informed  of  the  exact  conditions  under  which  manure 
may  become  injurious,  the  use  of  even  small  amounts  for  blueberries 
is  not  now  recommended. 

A  suggestion  may  be  made,  however,  as  to  a  possible  reason  for  the 
injury  of  blueberry  plants  by  manure.  In  the  glass-pot  experiment 
described  on  page  18,  in  which  plants  grown  in  a  mixture  containing 
half  as  much  manure  as  peat  made  exceptionally  good  growth  at  first 
in  it  soon  died,  the  death  of  the  plants  was  preceded  by  a  rotting  of 
the  roots.  Now,  manure  is  alive  with  myriads  of  bacteria,  while  peat 
contains  few.  An  examination  of  the  two  made  by  Mr.  Karl  F.  Kel- 
lerman,  from  samples  taken  from  the  kalmia  peat  and  the  cow  manure 
used  in  these  experiments,  showed  2,500  bacteria   per  plate  in  the 


Pig.   2G. — Spores  of  a  supposedly  injurious  fungus  in  the  epidermal  cells  of  blaeberry  roots. 

(Enlarged  GOO  diameters.) 

manure  and  70  to  150  in  the  rotted  peat,  each  plate  representing 
0.0004  of  a  gram  of  material.  The  bacteria  in  the  peat  were  chiefly 
of  two  species,  while  the  manure  contained  many.  It  is  a  reasonable 
supposition  that  the  rotting  of  the  blueberry  roots  may  have  been 
caused  or  aided  by  the  bacteria  in  the  manure  or  by  some  of  the 
fungi  with  which  manure  is  also  abundantly  charged.  In  mixtures 
like  those  recommended  by  McNab,  however,  containing  much  peat 
and  little  manure,  the  injurious  bacteria  and  fungi  in  the  manure  may 
have  been  killed  or  held  in  check  by  the  acids  that  exist  in  the  peat 
a  in  I  keep  such  organisms  in  control.  If  experiments  show  this  theory 
to  be  correct,  the  application  of  manure  to  blueberries  may  then  be 
made  intelligently. 

In  this  connection  it  may  be  well  to  call  attention  to  a  peculiar  spore 
found  in  the  roots  of  feeble  blueberry  plants  grown  in  unfavorable 
soils,  such  as  the  limed  peat  and  the  clayey  loam  described  on  pages 
23  and  24,  and  mixtures  containing  a  large  proportion  of  manure.  In 
some  of  the  epidermal  cells  of  the  rootlets  were  found  large  spherical 
bodies,  as  illustrated  in  figure  26.     They  usually  occurred  singly, 

193 


A.   SUPPOSEDLY    INJURIOUS   FUNG  65 

though  occasionally  two  ;in<!  rarelj  three  were  round  together  in  the 
same  cell.  Thej  were  0.0007  to  0.0008  of  an  inch  (18  to  20  ,- )  in 
diameter,  and  in  optical  section  showed  an  outer  ring  and  an  inner 
ring,  with  6,  7.  3,  '.'.  or  10  introrse  scallops  in  the  hyaline  zone  be- 
tween  them,  the  space  within  the  inner  ring  being  granular.  These 
are  evidently  spores  with  a  very  thick  wall,  marked  with  a  few  large 
pits  or  depressions,  and  granular  contents  in  the  cell  cavity.  I  n  what 
appeared  to  In'  later  stages  of  development  of  these  spores,  the  diam- 
eter was  slightly  larger,  the  wall  was  thin,  the  pits  had  disappeared, 
and  the  granular  content-  had  become  organized  into  minute  spher 
ical  bodies,  apparently  incipient  -warm  -pore-,  about  0.0001  of  an 
inch  {2  p)  in  diameter,  approximately  one-tenth  the  diameter  of  the 
spore  itself.  Several  of  these  large,  thin-walled  spores  had  put  out  a 
-hort  germination  tube  and  losl  their  content.-,  the  spore  remaining 
cut  irely  hyaline  and  empty. 

It  was  thoughl  at  first  that  these  might  be  the  reproductive  bodies 
of  the  mycorrhizal  fungus  of  the  blueberry,  but  a  careful  search 
failed  to  -how  any  connection  between  the  two.  It  was  observed, 
however,  that  in  the  rootlets  containing  the  spores  the  interior  cells 
usually  presented  a  diseased  appearance,  the  whole  rootlet  sometimes 
showing  a  brown  streak  down  it-  middle,  due  to  the  decomposition  of 
the  vessels  and  wood  cells.  The  inquiry  into  the  nature  of  the  spores 
was  not  pursued  further,  hut  the  conditions  strongly  suggested  that 
the  spore-  were  iho-c  of  a  para-it  ic  fungus  occupying  the  interior  of 
the  roots  and  causing,  or  associated  with,  their  death  and  decomposi- 
tion. The  spores  themselves  hear  a  strong  resemblance  to  the  resting 
spores  of  Asterocystis  radicis.a  parasitic  fungus  of  the  family  Chytri- 
diaceae.  This  fungus  occurs  in  Europe  in  the  root-  of  various  plant-, 
particularly  flax,  in  which  it  i-  the  cause  of  a  serious  disease." 

If  an  explanation  is  soughl  for  the  injurious  effeel  of  lime  on 
the  growth  of  the  blueberry,  the  observations  already  made  indicate 
the  propriety  of  a  careful  study  of  this  large-spored  fungus,  with 
special  reference  to  the  effect  of  lime  in  stimulating  it-  growth  and 
the  growth  of  the  other  organisms  of  decay  associated  with  it. 

(26)    POTS  CONTAINING  BLUEBERRY    plants  should  m    plunged  in   sand  or  other 

MATERIAL  THAT  WILL  FURNISH  CONSTAN1     MOISTUR1      VND  GOOD    DERATION 

AJthough  the  plunging  of  earthen  pots  nearly  to  the  rim  in  some 
moisture-holding  material, such  as  sand, sphagnum, or  peat. had  been 
practiced  for  various  purposes  in  several  of  the  earlier  cultures, 
and  had  been  found  essential  (as  stated  on  p.  60)  for  2-inch  pot 
cultures  if  rapid  and  uniform  growth  was  i<>  be  secured,  nevertheless 
the  importance  of  applying  the  same  practice  to  larger  pots  was  not 

rcbal.    Km  lie.     Recherches    BioloRiques    sur    une    Chytridinee    Parasite 
«hi  l .in.     Bulletin  de  I'Agrieiilture,  Brussels,  vol.  16,  1900,  pp.  "ill   554. 

5470.S       Bull    193      10 


66  EXPERIMENTS    IN    BLUEBERRY    CULTURE. 

appreciated  until  the  best  culture  from  the  11)08  seedlings  had  re- 
mained almost  stagnant  in  4-inch  pots  for  over  a  month.  The  con- 
dition of  the  plants  was  first  attributed  to  an  excess  of  acidity  in 
some  of  the  peat  used  for  potting,  and  next  to  the  necessity  of  a 
period  of  rest  from  active  growth.  Neither  of  these  reasons,  how- 
ever, it  was  ascertained  from  observation  of  other  cultures,  could 
account  except  in  part  for  the  distressed  condition  that  these  plants 
finally  reached. 

When  one  of  the  plants  was  knocked  out  of  its  pot  it  was  in- 
variably found  that  a  large  part  of  the  roots  at  the  side-,  of  the 
earth  ball  were  dead.  It  was  at  the  period  of  the  year.  April  and 
May.  when  the  advent  of  warm  sunny  days  made  the  control  of 
temperature  in  the  greenhouse  somewhat  difficult,  and  this,  together 
with  the  previous  rapid  growth  of  the  plants  and  the  consequent 
increase  of  their  water  consumption,  had  brought  about  considerable 
irregularity  in  the  moisture  content  of  the  pots.  The  conclusion  was 
reached  that  the  walls  of  the  pots  had  become  dry  on  one  or  more 
occasions,  and  that  this  had  killed  the  delicate  roots  that  came  in 
contact  with  them.  The  roots  of  the  blueberry,  as  described  on 
page  42,  are  exceedingly  slender,  the  smallest  being  about  two- 
thousandths  of  an  inch  in  diameter.  They  are  very  quickly  killed 
by  drying. 

On  the  basis  of  this  conclusion  the  general  practice  of  plunging 
blueberry  pots  was  adopted.  If  the  plants  are  to  be  exposed  to  a 
very  warm,  dry  atmosphere  the  plunging  should  be  done  before  any 
considerable  quantity  of  roots  has  grown  through  the  soil  to  the  wall 
of  the  pot.  It  is  probably  still  better  to  do  the  plunging  imme- 
diately after  the  potting.  Tor  then  uniform  moisture  conditions  can 
he  secured  throughout  the  soil  in  the  pot. 

Besides  the  avoidance  of  injury  to  the  plants  l>y  the  drying  of  their 
root-,  the  practice  of  plunging  has  another  marked  advantage,  the 
maintenance  of  a  moderate  but  adequate  and  even  optimum  degree  of 
moisture  in  the  soil  with  infrequent  waterings.  A  series  of  pots 
plunged  in  live  sphagnum  in  a  cool  greenhouse  during  the  winter  of 
L908-9  frequently  went  for  a  week  at  a  time  without  requiring  water 
and  i  hen  most  of  the  water  was  applied  between  instead  of  in  the  pots. 
The  moisture  evidently  moves  freely  in  or  out  through  the  wall  of 
the  pot.  which  is  of  course  not  glazed,  and  an  excess  or  deficiency  in 
any  one  place  is  soon  adjusted. 

Sand  has  been  found  a  convenient  and  satisfactory  plunging  ma 
terial.  The  surface  of  the  sand  should  come  to  the  same  level  as  the 
soil  in  the  pot,  or  a  little  above  it.  A  little  sand  on  the  surface  of  the 
-oil  does  no  harm,  and  indeed  is  probably  advantageous.  When  a 
single  pot  is  to  he  plunged  il  may  he  done  by  placing  it  within  another 
193 


Ml    I  huh    '  .1     OUTDOOR    i    I    I.  I  I'KI      IN     POTS.  67 

pol  of  •_'  inches  larger  diameter,  the  space  between  the  walls  of  the 
two  pots  being  then  filled  with  sand.     (See  PI.  XVIII.) 

The  practice  of  plunging  has  proved  to  lie  of  (he  greatest  im- 
portance in  securing  ;i  large  growth  in  potted  blueberry  plants,  as 
will  lie  appreciated  from  the  description  of  the  development  made 
under  such  conditions  out  of  doors  in  the  summer  of  1909.  (  See  p. 
68.)  In  that  description  special  attention  i-  drawn  to  (lie  superior 
conditions  of  aeration  in  plunged  pots. 

(27)  Plants  >>i    thi    swamp  blueberr>    sometimes  lai    down   flowering  buds 

\  i    i  ii  i    m.i    hi    seven    months. 

The  laying  down  of  flowering  buds  is  discussed  in  detail  on  pages 
71  to  "•">.  where  a  descript  ion  i-  given  of  the  general  occurrence  of  this 
phenomenon  in  vigorous  plants  one  year  old.  The  first  flowering 
buds,  however,  appeared  much  earlier.  They  were  observed  on  April 
8,  1909,  on  plants  which  were  in  day-  less  than  7  months  old.  At  the 
end  of  the  7  months  ■_' I  plants  out  of  258,  which  constituted  seven  of 
the  mosl  advanced  cultures  from  the  seedlings  of  L908,  had  laid  down 
flowering  buds.  A  small  percentage  of  the  seedlings  of  1907  had  also 
laid  down  flowering  buds  at  about  the  same  age.  The  phenomenon 
ma\   therefore  he  regarded  as  not  rare  in  vigorous  plant-  of  thi--  age. 

These  flowering  buds,  which  contain  the  rudiment-  of  about  7  to  12 
flowers  each,  are  not  adapted  to  development  into  clusters  of  flowers 
until  they  have  been  subjected  to  a  period  id'  cold.  Most  of  the  buds. 
therefore,  forming  just  a-  warm  weather  was  approaching,  withered 
and  dried  on  the  bushes.  A  few  flowered  in  L908  and  in  1909,  and  in 
thi-  latter  year  one  plant  hole  ripe  fruit  on  August  25,  at  the  age  of  a 
lilt  le  more  than   1  1    months. 

(28)  l\      III!      SPRING     Mill:     llll      DANGEB    01      FROS1     WAS     PAS!     THE    PLANTS    WERE 

Kl  POTTED    AMI    PLACED  HIT   OF   DOORS,    IN     II  Ml     SHADE,    PLUNGED    IN    SAND. 

On  May  1'.'  to  22,  L909,  the  seedlings  of  1'.'"-  were  repotted  in  6-inch 
pots,  iii  a  mixture  in  mo-t  cases  of  peat  8,  -and  1.  and  loam  1.  and 
placed  outdoor-.  The  plants  in  the  principal  culture-  had  at  thi-  time' 
an  average  height  of  about  !•  inches,  with  a  maximum  of  15  inches. 
The  pot-  were  plunged  in  sand.  Thej  were  in  a  situation  where  they 
were  exposed  to  sunlight  from  aboul  8  o'clock  in  the  morning  to  5 
o'clock  in  the  afternoon,  and  to  protecl  them  from  too  great  heat  they 
were  partiaJlj  sheltered  by  a  -hit  shade.  The  slat-  were  •_'  inches 
wide,  with  2-inch  openings  between.  A-  the  sun  struck  the  slats 
somewhat  diagonally  and  they  were  half  an  inch  thick,  the  plants 
when  covered  by  the  -hade-  received  a  little  less  than  half  sunlight. 
On  clear  day-  the  -hade-  were  kept  over  the  plant-  from  9  o'clock 
lo  I  o'clock.  At  other  hour-  and  on  cloudj  days  the  -hade-  were 
removed.     On  August  •_'."•  the  time  of  shading  was  shortened  to  the 

103 


68  EXPERIMENTS    IN    BLUEBERRY    CULTURE. 

period  between  in  and  3  o'clock,  and  after  September  12  the  shades 
were  Left  off  altogether. 

The  plants  were  watered  with  a  swift  spray  from  a  hose,  the  water 
being  applied  only  when  necessary  to  keep  the  soil  from  actually 
drying  out.  The  sand  between  the  pots  was  seldom  allowed  to  become 
dry  to  the  depth  of  more  than  half  an  inch.  A  sand  mulch  of  about 
a  quarter  of  an  inch  on  the  top  of  the  soil  in  the  pot  was  found  useful 
in  preventing  the  rapid  drying  of  the  soil  by  direct  evaporation. 

1-1)1  I'.V  THE  USE  OF  THE  CULTURAL  METHODS  ALREADY  DESCRIBED,  SEEDLINGS  OE 
THE  SWAMP  BLUEBERRY  HAVE  BEEN  CROWN  INTO  ROBUST  PLANTS  OF  A  MAXI- 
MUM HEIGHT  01  TWENTY-SEVEN  INCHES  AT  TWELVE  MONTHS  FROM  GERMINA- 
TION. 

The  growth  of  the  plants  out  of  doors  during  the  summer  was 
remarkably  vigorous.  Hitherto  experimenters  with  seedling  blue- 
berries have  been  able  to  produce  only  comparatively  small  plants  at 
the  end  of  the  first  season,  as  shown  by  the  following  citation  from  a 
publication  of  the  best -known  experimenter:" 

The  blueberry  makes  much  less  growth  the  lirst  two  years  from  seed  thin 
the  huckleberry,  but  grows  faster  afterward.  The  third  year  I  have  had  them 
make  a  growth  of  (5  to  S  inches.  The  low  blueberry  and  huckleberry  begin  to 
bear  at  •">  or  4  years,  while  the  high-bush  blueberry  requires  4  to  6  years. 
From  1   to  :!  inches  growth  the  first  year  is  about  all  you  can  expect. 

Under  the  system  of  treatment  described  in  the  present  bulletin 
seedlings  have  been  grown  to  a  height  of  -~  inches  at  twelve  months 
from  germination.  Out  of  the  seedlings  of  L908,  250  were  carried 
through  to  the  close  of  the  season  of  L909  in  6-inch  pots.  Of  these.  1.'. 
were  stunted  plants.  The  remaining  235  had  an  average  height  at 
the  end  of  the  season  of  exactly  L8  inches.  The  larger  stem-  were 
often  a  quarter  of  an  inch  in  thickness,  and  the  main  trunk,  half  sub- 
merged in  the  ground,  sometimes  reached  a  diameter  of  half  an  inch. 
The  general  appearance  of  these  plants  is  shown  in  Plate  VIII. 

The  principal  feature-  of  cultural  treatment  which  have  contributed 
to  this  development  are  (a)  the  autumn  germination  of  the  seeds, 
(b)  the  use  of  suitable  acid  soils,  (<-•)  the  plunging  of  the  pots,  and 
(d)  the  partial  shading  of  the  plant-  during  the  heat  of  summer,  the 
application  of  these  cultural  methods  having  been  guided  throughout 
by  the  discovery  of  the  existence  of  a  mycorrhizal  fungus  in  these 
plants  and  its  treatment  as  essential  to  their  nutrition.  The  system 
of  germination  and  the  character  of  the  soil-  used  have  already  been 
described  in  detail.  The  exact  effects  of  the  plunging  and  the  shading 
remain  to  be  considered. 

It  has  already  been  shown  (p.  66)  that  when  a  plant  is  not 
plunged,    (he    minute    rootlets   that    lie   against    the   -ides   of   the    pot 

"Dawson.  Jackson.     Cultivator  and  Countrj   Gentleman,  vol.  50,  1885,  p.  G60. 
193 


Bui.  193.  Bureau  of  Plant  Industry,  U.  S.  Dept.  of  Ag 


Plate   VIII. 


«     I      nl       I'l    l;l.     IT   \  I      IN      I'l.l"  Mil   |i     I'n  I  : 


69 


are  very  liable  to  death  from  dryness.  When  the  pot  is  plunged  in 
sand  and  the  sand  is  kept  moist  these  rootlets  can  not  die  from 
drought.  They  keep  on  growing  until,  in  the  ease  of  vigorous  plain-. 
when  the  earth  !>al!  is  knocked  from  the  pot,  the  soil  ran  not  be  seen 
because  of  the  dense  mat  of  live  roots  that  line  the  pot.  The  same 
thick  mass  of  live  roots  was  developed  in  a  scries  of  1907  seedling- 
carried  over  the  winter  of  l'-(<is  '.i  in  the  greenhouse  in  pots  plunged 
in  sphagnum.  When  the  pot  is  surrounded  by  the  moist  plunging 
material  these  roots  continue  to  luxuriate  for  months  longer  than 
llic\  otherwise  would.  They  evidently  find  the  aeration  conditions, 
as  well  ;i>  tlir  moisture  conditions,  at  the  wall  of  the  pot  very  satis 
fa<  tory,  for  the  development  of  roots  there  is  far  greater  than  within 
the  ball  itself. 

The  highlj  efficient  aeration  at  the  wall  of  plunged  pots  may 
explain  one  use  of  soils  in  which  the  results  of  the  present  investigii 
lion-  do  nut  agree  with  the  practice  of  the  old  heath  growers.  In 
one  culture  of  25  plants  tlm  soil  used  in  the  first  potting  was  pure 
rotted  kalmia  peat  rubbed  through  a  quarter-inch  screen.  This  firsl 
potting,  in  1-inch  pot-,  was  done  on  March  20.  1909.  The  repotting. 
in  6-inch  pots,  was  (lone  on  May  22,  1909,  in  the  same  kind  of  soil, 
pure  coarsely  sifted  kalmia  peat.  These  plants  grew  to  be  the 
largest  of  any  of  the  seedlings  of  1908.  their  average  height  at  the 
close  of  the  season  being  -J0..~.  inches.  The  three  plants  shown  in 
Plate  IX.  all  over  •_' I  indie-  in  height  and  one  of  them  27  inches. 
w ere  from  t his  cult ure. 

The  use  of  pure  peat  was  not  advocated  by  the  old  heath  growers. 
McNah  recommended  a  mixture  of  !  oi  5  part-  of  peat,  by  bulk,  to 
I  of  -and.  and  an  even  larger  pi'oportion  of  sand.  2  parts  out  <>!'  •"'. 
has  been  recommended  b\  Dawson  for  blueberries.  When  the  pots 
are  not  plunged  and  do  not  therefore  have  the  advantage  of  the 
superb  aeration  conditions  foHnd  at  the  wall  of  the  pol  when  sur 
rounded  by  moist  -and.  it  i>  probable  thai  the  presence  of  consider- 
able -and  in  the  soil  is  necessary  to  secure  adequate  aeration  of  the 
interior  of  the  earth  ball,  for  unless  the  pot  is  plunged  most  of  the 
rootlet-  that  lie  against  the  sides  of  the  pot  will  be  killed  and  the 
plant  nin-i  rely  for  it-  chief  nourishment  on  the  roots  in  the  interior 
of  the  ball. 

That  the  necessity  for  interim  aeration  in  the  pots  is  greal  in  the 
case  of  heaths,  if  the  plant-  are  not  plunged  or  are  not  frequently 
repotted,  is  shown  by  a  peculiar  and  interesting  cultural  practice 
long  tried  and  highly  recomniended  by  McNab.  This  practice  is 
the  distribution  of  broken  crocks  or  pieces  of  sandstone  through  the 
-oil  at  the  time  of  repotting.  He  found  by  experience  thai  the  prac 
(ice  was  highly  advantageous  t<>  the  plants,  nnd  although  he  did  not 
directly  explain  his  success  in  such  a  way,  there  is  little  doubt  thai 


70  EXPERIMENTS   IN    BLUEBERRY    CULTURE. 

his  method,  which  may  be  regarded  as  a  substitute  for  plunging,  was 
advantageous  because  it  gave  large  aeration  surfaces  about  the  stones 
in  the  interior  of  the  earth  ball  and  provided  a  place  there  for  a  large 
development  of  roots  which  could  not  take  place  at  the  wall  of  the 
pot.     McNab's  description  of  his  method  of  repotting  is  as  follows: 

In  shifting  heaths  I  never  reduce  the  old  ball  of  earth  more  than  by  rubbing 
the  sides  and  bottom  with  the  hand,  so  as  to  loosen  the  outside  libers  a  little. 
I  have  often  shifted  heaths  twice,  and  even  three  times,  in  the  course  of  the 
spring  and  summer,  with  the  greatesl  success.  It  is.  however,  quite  unnecessary 
to  shift  a  heath  until  the  young  fibers  have  come  through  the  fresh  earth  given 
to  it  at  its  previous  shifting,  and  begun  to  extend  themselves  round  the  inner 
edge  of  the  pot  or  tub:  but  as  soon  as  this  lakes  place,  they  may  then  lie  shifted 
with  advantage.  This  frequent  shifting,  however,  is  quite  unnecessary,  unless  it 
be  to  encourage  a  favorite  specimen;  for  in  all  ordinary  cases,  particularly 
when  the  plant  is  large.  I  consider  one  good  shifting  in  two  or  three  years  quite 
sufficient.     *     *     * 

Besides  the  compost  and  draining  which  1  have  already  mentioned,  when  I 
begin  to  shift  heaths  I  have  always  at  hand  a  quantity  of  coarse,  soft  free 
stone,  broken  into  pieces,  front  an  inch  to  4  or  5  inches  in  diameter.  Of  these 
I  always  introduce  a  quantity  among  the  fresh  earth  as  it  is  put  into  the  pot  or 
tub.  round  the  old  ball  of  earth  about  the  plant,  and  press  them  well  down 
among  fresh  earth  as  it  is  put  in.  This  I  consider  of  great  advantage  to  all 
sorts  of  heaths,  1ml  more  particularly  so  to  those  that  may  have  been  shifted 
into  a  much  larger  pot  or  tub  at  once  than  what  it  bad  been  grown  in  before,  or 
in  what  I  would  call  biennial  or  triennial  shifting.  These  pieces  of  stone  may 
be  put  in  as  large  as  the  opening  will  admit  between  the  old  ball  and  the  edge 
of  the  pot.  In  some  of  our  largest  tubs  this  opening  is  full  4  inches  wide,  and 
where  much  earth  is  required  to  be  put  in  the  bottom  over  the  draining  before 
the  plant  is  put  in.  a  quantity  of  these  stones  should  be  mixed  with  the  earth 
also.  I  likewise  use  occasionally  large  pieces  of  soft  burnt  broken  pots,  put 
anion:.'  the  earth  in  the  same  way  as  the  stones:  but  I  prefer  stones  when  I  can 
procure  them  soft  and  free  of  iron.  The  quantity  of  stones  which  I  introduce 
along  with  a  large-sized  heath  at  shifting,  will,  in  most  cas-s,  if  broken  down 
into  sand,  and  added  to  the  sand  previously  in  the  soil,  form  about  one-third 
part  of  the  whole  mass.  When  stones  are  introduced  among  the  earth  in  the 
w:i\  I  have  recommended,  heaths  will  never  suffer  so  much  in  the  summer  from 
occasional  oeglect  to  water  them  as  they  would  do  if  the  stones  were  QOt  intro 
duced,  because  these  stones  retain  the  moisture  longer  than  the  earth,  and  in 
the  winter  they  allow  a  freer  circulation  of  any  superabundant  moisture  which 
may  be  given  through  the  mass. 

The  effect  of  the  half  shade  used  over  the  blueberries  during  the 
summer  of  L909  was  to  make  (he  growth  of  the  plants  continuous 
instead  of  confining  it  to  a  brief  period  in  the  early  part  of  the  season. 
In  a  wild  state  the  twigs  of  blueberry  plants  stop  growing  in  early 
summer,  the  stoppage  being  indicated  by  the  withering  of  the  upper 
most  leaf  rudiment.  The  less  vigorous  twigs  stop  first,  (he  more 
vigorous  ones  next,  and  the  shoots  last.  Stoppage  of  growth  is  has- 
tened by  hot  dry  weather  and  is  deferred  by  cloudy  humid  weather. 
In  the  latitude  of  Washington  stoppage  of  ordinary  twig  growth  in 
wild  plants  of  Vactinium  <ttrococcum  begins  in  May  and  is  usually 

193 


3ul.  193.  Bureau  of  Plant  Industry,  U.  S.  Dent  of  Agriculture. 


Plate  IX. 


PARTIAL  SHADE    ADVANTAGEOUS.  71 

completed,  excepl  on  vigorous  shoots,  in  June.  In  some  of  the  culti 
vated  plants  which  were  nol  shaded  growth  was  similarly  stopped  by 
the  ;ul\t'ii(  of  hot  weather.  In  the  plants  under  the  slal  shades,  how 
ever,  vigorous  stems  did  nol  wither  their  tips  until  their  normal 
growth  had  run  its  course,  and  as  new  shoots  were  continually  start- 
ing there  was  no  general  stoppage  of  growth  until  September,  and 
many  of  the  plants  continued  to  grow  throughoul  that  month. 

The  shade  was  not  great  enough  to  "draw"  the  plants;  that  is, 
to  make  their  growth  spindling  through  a  stretching  up  for  light. 
It  was  merely  sufficient  to  prevent  excessive  heat  and  destructive 
transpirat  ion. 

<  :',H  I   'I'll!     FLOWERING    BUDS   OF   THE    BLUEBERRY    ARE    PRODUCED    I'.Y    1111      rRANSFORMA- 
riON  OF  DORMANT  I.EA1     BUDS  IN     1111     LATTER  PART  01     Mil     SEASON. 

The  flowers  and  leaves  of  the  swamp  blueberry  arc  produced  in 
the  spring  from  separate  buds,  and  these  buds  are  formed  in  the 
preceding  year.  The  two  kinds  of  buds  arc  conspicuously  different, 
a-  may  be  -ecu  by  the  accompanying  illustration.  (1M.  X.  fig.  1.) 
The  leaf  buds  occupy  the  lower  part  of  the  twig.  They  are  small, 
:al,  about  0.08  to  0.12  of  an  inch  (2  to  3  mm.)  long,  with  2  to  I 
external  scales  about  equaling  each  other  in  length  and  each  ending 
in  a  sharp  point.  The  points  only  of  the  interior  scales,  which  are 
of  similar  length,  are  visible.  When  a  leaf  bud  develops  in  the 
spring  ii  produces  a  leafy  twig. 

The  flowering  buds  are  borne  along  the  upper  pari  of  the  twig. 
They  are  fat.  ovoid  -tincture-,  commonly  0.15  to  ().:'>  of  an  inch 
(3.5  to  7  mm.)  long,  several  times  larger  than  the  leaf  buds.  They 
-how  ordinarily  in  to  1">  external,  broad,  overlapping  scales.  Each 
flowering  laid  contain-  the  rudiments  of  a  raceme  of  usually  7  to  L2 
flowers,  the  hud  of  each  <d'  these  Mowers  lying  iii  the  axil  of  a  bract 
and  bearing  two  bractlets  below  the  middle  of  its  short  pedicel. 
When  a  flowering  bud  develops  it  produces  a  raceme  of  (lowers,  hut 
no  accompanying  twig  or  leaves. 

Leaf  hud-  are  always  axillary  and  flowering  hud-  almosl  always 
-o.  The  hud  at  the  summit  of  a  twig  i>  in  reality  situated  in  the 
axil  of  the  uppermost  leaf,  except  in  the  rare  cases  in  which  the  twig 
lip  doe-  not  wither  when  it  stops  it-  growth.  In  such  cases  a  true  ter- 
minal hud  i-  formed,  surrounded  by  a  group  of  lateral  buds  in  the 
axils  of  bracts.  So  far  a-  observed  these  buds  are  always  flowering 
hud-  and  are  produced  mi  the  end-  of  vigorous  shoots. 

The  manner  in  which  the  plants  lay  down  their  flowering  buds, 
through  the  transformation  of  leaf  hud-,  is  very  interesting,  and  it 
im;i\  prove  to  have  a  bearing  <>i'  some  importance  on  the  method  and 
time  of  pruning  the  bushes.  The  form  of  the  leaf  buds  ha-  already 
been  described.    They  appear  singly  in  the  axils  of  the  leaves  almost 

103 


7'2  EXPERIMENTS    IN    BLUEBERRV    CULTURE. 

as  soon  as  the  leaf  is  fully  developed.    After  a  few  weeks  the  external 

scales  of  the  bud  turn  brown  and  the  bud  then  goes  into  a  condition 
of  dormancy,  unless  it  is  forced  into  growth  through  an  injury  to  the 
twig  or  some  other  unusual  circumstance.  In  most  of  the  buds  this 
dormant  condition  continues  through  the  summer,  fall,  and  winter. 
If  the  plant  is  in  condition  to  lay  down  flowering  buds,  however,  a 
new  sort  of  activity  appears  in  the  late  summer  or  autumn.  One  or 
mote  of  the  leaf  buds  near  the  end  of  a  twig  start  to  grow.  The  two 
brown  scales  are  spread  apart,  new  green  scales  appear  between  them, 
and  a  large,  bit.  flowering  bud  is  formed.  The  bud  does  not.  how- 
ever, continue  its  growth  at  this  time,  but  its  green  new  scales  turn 
brown  and  the  condition  of  dormancy  is  again  resumed  before  cold 
weather  comes  on. 

The  flowering  buds  thus  develop  out  of  buds  which  ari'  in  no  way 
distinguishable  from  leaf  buds.  They  are,  in  fact,  leaf  buds  until 
their  transformation  takes  place,  and  except  for  such  transformation 
they  would  remain  leaf  bud-.  Furthermore,  it  has  been  found  ex- 
perimentally that  after  the  formation  of  flowering  buds  has  been 
completed,  leaf  buds  still  lower  on  the  twig  can  be  forced  by  suitable 
treatment  to  transform  themselves  into  flowering  buds.  Such  an  ex- 
periment was  made,  as  follows: 

( )n  August  •_'!.  1909,  at  Lanham,  Md.,  a  vigorous  bush  of  Vaccinium 
atrococcum  was  selected,  which  had  already  laid  down  it--  flowering 
buds  for  the  succeeding  year.  Two  branches  of  nearly  equal  size, 
about  1C>  inches  long,  one  with  14  twigs  and  53  (lowering  bud-,  the 
other  with  16  twigs  and  IS  flowering  buds,  were  chosen  for  the  ex- 
periment. On  the  branch  containing  the  18  flowering  buds  each  twig 
was  cut  oil'  at  a  point  between  its  lowermost  flowering  bud  and  its 
uppermost  leaf  bud,  with  the  object  of  ascertaining  whether  any  of 
I  he  leaf  buds  on  the  stub  of  the  twin'  would  transform  themselves 
into  flowering  buds.  The  other  branch  was  left  unpinned  as  a  check. 
to  show  whether  the  normal  laving  down  of  flower  buds  had  in  reality 
been  completed  on  August  "24.  On  October  1,  1909,  the  two  twig-  were 
again  examined.  The  pruned  branch  had  laid  down  :'>1  new  flowering 
buds,  which  in  all  cases  were  the  transformed  upper  leaf  buds  on  the 
-lulis  of  the  twigs.  On  the  check"  branch  only  1  new  flowering  bud 
had  been  laid  down. 

The  best  method  of  pruning  the  swamp  blueberry  is  yet  to  he 
devised,  hut  if  a  superficial  pruning,  like  that  of  a  hedge,  prove-  to 
be  a  good  method  of  stimulating  vigorous  growth,  it  is  evident  from 
this  experiment  that  the  most  advantageous  time  to  do  the  prun- 
ing, if  a  crop  i-  to  be  secured  the  next  year,  is  after  the  berries  are 
gathered  and  about  the  time  when  the  bush  is  forming  it-  next  year's 
flowering  buds.  It  will  then  lay  down  new  flowering  buds  on  the 
cut  stubs.  If  the  pinning  were  done  in  late  autumn,  in  the  winter, 
193 


Bui.  193.  Bureau  of  Plant  Industry.  U.  S.  Dept.  of  Agriculture. 


Plate  X. 


\\  I  Kl  NG     Bl   l>s    FORM  |,|,    l  \     |    \  |  i     Sl'MMI  R.  73 

or  m  the  spring,  no  nr«  flowering  buds  would  be  formed  to  replace 
those  removed  bj  i  he  pruning. 

The  time  of  laying  down  flowering  buds  seems  to  lie  correlated  with 
the  length  id'  die  growing  season.  About  Washington  V actinium 
atrococcum  begins  to  form  its  flowering  buds  in  the  latter  pari  of  Au- 
gust, one  to  two  months  after  its  berries  are  mat ured.  In  Vact  inium 
pallidum,  on  the  high  mountain  summits  of  North  Carolina,  where 
the  growing  season  is  short,  the  transformation  of  leaf  buds  into 
flowering  buds  begins  as  early  as  the  la.-i  week  in  July  while  some 
of  the  berries  are  -till  preen.  In  the  cultivated  plant-  at  Washing- 
ton the  formation  of  flowering  buds  did  not  begin  in  1909  until  Sep- 
tember, and  it  continued  on  some  plants  until  cold  weather  stopped 
t  heir  grow  th. 

The  laying  down  of  flowering  buds  appears  to  be  a  phenomenon 
local  within  the  twig.  Cuttings  of  the  swamp  blueberry  made  in 
New  Hampshire  on  July  9,  L909,  transformed  their  leaf  buds  into 
flowering  buds  in  the  cutting  bed  after  reaching  Washington,  as 
shown  in  Plate  X.  figure  l'.  but  whether  the  transformation  in  this 
ease  was  made  before  or  a  tier  the  cutting  had  rooted  was  not  observed. 
In  another  case,  however,  that  of  cuttings  made  in  New  I  lamp-hire 
September  11.  1909,  from  long  late  shoots  bearing  only  leaf  hud-. 
the  transformation  into  flowering  buds  began  to  occur  in  the  cutting 
bed  October  L2  and  was  completed  before  any  roots  had  formed, 
i   PI.  X.  fig.  3.) 

l.'ill.Vl      III!      END    OF     I  Mill:     FIRS!      YEAR     SEVENTH      PER    'INI     OB      I  111      BLUEBERRY 
PI    Wis    II  \\<   1   \lli   DOWN  FLOWERING  BUDS  FOR  Till    [»EXT  SPRING'S  BLOSSOMING. 

At  the  end  of  the  season  of  1909,  177.  or  7')  per  eont.  of  the  250 
seedlings  of  1908  that  had  been  put  in  6-inch  pots  had  developed 
flowering  buds.  In  Plate  XI  i-  shown  one  of  these  seedlings,  pho- 
tographed on  November  •_'.  1909,  which  had  laid  down  12  flowering 
hud-.  One  plant  produced  ">v  flowering  hud-.  At  the  end  of  the 
preceding  season,  1908,  al  leasl  25  per  cent  of  the  seedlings  of  l'.»07 
that  were  still  kept  in  pots  hail  produced  flowering  buds.  Therefore, 
notwithstanding  the  statements  of  earlier  experimenters  that  the 
seedlings  of  this  species  <h>  not  fruit  until  they  are  several  years 
old  (p.  08).  it  i-  regarded  a-  established  that  under  the  culture  system 
worked  out  by  these  experiments  a  substantial  percentage  will  lay 
down  flowering  buds  at  the  end  of  the  first  year  and  will  bear  fruit 
the  second  year. 

Attention  has  already   I n  called   (p.  67)  to  the  occasional  laying 

down  of  flowering  buds  when  the  seedlings  were  only  7  month-  old, 
followed  rarel\  l>\  flowering  and  fruiting  at  the  age  of  less  than 
i  year. 

103 


74  EXPERIMENTS    IN     BLUEBERRY    CULTURE. 

(32)  Plants  of  the  swamp  blueberry  are  exceedingly  hardy  and  pass  the 
winter  in  good  condition  outdoors  when  the  soil  is  covered  merely 
with  an  oak-leaf  mulch,  but  when  not  exposed  to  outdoor  condi- 
tions they  do  not  begin  their  growth  in  spring  in  a  normal  ma.w1  b. 

During-  the  fall,  winter,  and  early  spring  of  1908-9  a  series  of  blue- 
berry seedlings  of  1907  was  kept  outdoors  on  a  south  window  sill  to 
ascertain  whether  repeated  freezing  and  thawing  would  kill  them. 
Most  of  the  plants  were  in  thin  glass  3-inch  pots,  covered  at  the  sides 
with  one  thickness  of  gray  blotting  paper.  One  plant  (to  which 
reference  is  again  made  on  pp.  75  and  7G)  was  in  a  5-inch  earthen 
pot.  None  of  the  plants  were  mulched  or  covered  in  any  way.  They 
were  watered  whenever  necessary  to  keep  the  soil  from  drying.  In 
cold  weather  the  air  circulated  freely  about  the  pots  and  the  soil  was 
repeatedly  frozen  solid.  On  warm,  sunny  days  the  melting  of  the  ice 
look  place  rapidly.  Hard  freezing  followed  by  quick  thawing  was 
many  times  repeated,  and  the  conditions  of  exposure  were  such  that 
the  plants  undoubtedly  were  subjected  to  a  severer  test  for  hardiness 
than  they  would  ever  receive  under  cultural  conditions. 

The  plants  passed  the  winter  without  losing  any  of  their  twigs. 
The  wood  was  plunrp  and  in  excellent  condition  when  spring  came. 
as  was  evidenced  further  by  the  remarkable  uniformity  with  which 
every  dormant  bud  started  to  grow  after  the  first  few  warm  days. 

For  the  roots  of  some  of  the  j^lants  in  glass  pots,  however,  the 
exposure  was  too  severe.  In  some  of  the  glass  pots  no  root  growth 
followed  the  starting  of  the  twigs,  and  the  plants  finally  died.  In 
others  the  root  growth  at  first  was  feeble  and  the  plants  lost  some  of 
their  newly  started  twigs  by  withering.  Most  of  the  plants,  however, 
including  the  one  in  the  5-inch  earthen  pot,  made  normal  growth  of 
both  twigs  and  roots,  notwithstanding  the  extraordinarily  severe 
treatment  to  which  they  had  been  subjected.  No  difficulty  is  antici- 
pated, therefore,  in  wintering  blueberry  plants  successfully  out  of 
doors  under  any  ordinary  cultural  conditions.  The  seedlings  of  1908 
covered  with  oak  leaves  in  their  outdoor  plunging  bed  of  sand  passed 
the  winter  of  1909-10  in  good  conditio]). 

That  blueberry  plants  must  be  subjected  to  some  sort  of  exposure, 
if  they  are  to  start  satisfactorily  in  the  spring,  is  indicated  by  the 
behavior  of  certain  seedlings  of  1907  which  were  carried  through  the 
winter  of  1908-9  in  a  rose  house,  where  the  temperature  at  night  was 
about  G0°  F.  and  during  the  day  about  10  degrees  higher.  These 
plants,  although  subjected  to  most  persistent  coaxing,  absolutely 
refused  to  grow  during  (he  the  five  months  from  November  to  March, 
although  newly  germinated  seedlings  grew  luxuriantly  under  exactly 
the  same  conditions. 

The  comparison  of  these  indoor  plants  with  outdoor  plants  may 
best  be  made  by  an  examination  of  the  buds  shown  in  the  accompany- 

193 


Bui.  I  93,  Bureau  of  Plant  Industry,  U.  S.  Dept.  of  Agriculture. 


Plate  XI. 


PLANTS  I"  BE  WINTERED  OUTDOORS.  75 

ing  illustrations,  made  from  typical  indoor  and  outdoor  specimens. 
The  photographs  reproduced  in  Plate  XII  were  made  on  March  l'7. 
L909.  The  plant  shown  in  figure  1  of  this  plate  was  a  seedling  of 
September,  L907,  which  had  been  kept  in  a  greenhouse  all  it-  life  at 
a  temperature  suited  to  the  growing  of  roses.  The  plant  shown  in 
Plate  XII,  figure  2,  was  identical  in  history  with  the  other  until 
October  20,  L908,  when  it  was  placed  outdoors  and  exposed  to  the 
severest  winter  conditions.  It  was  one  of  the  window-sill  plants  de- 
scribed on  pane  74.  The  leaves  shown  on  the  indoor  plant  |  PI.  XII, 
fig.  I)  are  those  formed  in  the  summer  of  L908,  which  by  reason  of 
the  warm  temperature  of  the  greenhouse  in  which  the  plant  was 
wintered  had  never  fallen  off,  although  the  plant  had  made  no  growth 
later  than  October,  L908.  Neither  a  flowering  hud  nor  a  leaf  hud 
has  started  on  this  plant.  On  the  outdoor  plant  (PI.  XII.  fig.  2) 
the  I  flowering  buds  and  62  leaf  buds  which  had  lain  dormant  dur 
ing  the  winter  had  begun  to  push  a  few  day-  before  the  picture  was 
taken. 

Plate  XIII,  from  photographs  taken  on  April  24,  1909,  -hows  the 
same  two  plants  nearly  a  month  later.  The  leaf  buds  on  the  outdoor 
plant  (PI.  XIII.  fig.  2)  ha\e  grown  into  leafy  twigs  and  the  flower- 
ing buds  are  fully  opened.  Of  the  dormant  buds  on  the  indoor 
plant  (PI.  XIII.  hi:,  n  only  two  have  -tailed  to  grow.  Of  these 
two  new  twigs,  one  on  the  stem  to  the  left,  in  the  axil  of  the  third 
leaf  from  the  top.  ha-  withered  it ~  tip  and  -topped  developing  before 
making  a  full-sized  leaf.  The  other  new  twig,  on  the  stem  to  the 
right,  developed  abnormally  from  the  axil  of  a  basal  bract  of  a 
flowering  hud.  It  later  made  g I  growth  and  became  a  very  vigor- 
ous -hoot.  All  the  flowering  buds  on  this  plant  dried  up  and  pro- 
duced no  flowers. 

The  erratic  starting  of  dormant  plant-  which  have  not  been  sub- 
jected in  the  conditions  necessary  to  bring  them  out  of  their  dor- 
mancy in  a  normal  manner  i-  well  shown  also  in  Plate  XIV.  This 
illustration  is  from  a  photograph  taken  February  Is.  L909.  The 
plant  was  a  seedling  of  September,  L907,  which  was  brought  into  the 
greenhouse  in  early  December,  l'.K)S.  and  remained  there  during  the 
winter.  The  illustration  shows  that  only  one  of  the  two  flowering 
buds  on  the  upper  twig  has  started,  one  of  the  four  on  the  lower 
twig,  and  none  of  the  lea  f  hud-. 

There  can  be  no  question  thai  for  ordinary  purposes  blueberry 
plant-  should  be  wintered  outdoor-.  If  it  is  desired  in  experimental 
work  to  force  blueberry  plants  to  fruit  in  a  greenhouse  during  their 
second  winter,  it  will  be  necessary  cither  to  etherize  them  or  to  find 
out  some  other  method  of  treatment  by  which  the  starch  in  their 
twigs  can  be  transformed  into  other  carbohydrates  available  for  the 
building  up  of  new    plant   tissues.     The  writer  believes  that   in  the 

193 


7(>  EXPERIMENTS    IX    BLUEBERRY    CULTURE. 

hard-wooded  deciduous-leaved  tree-  and  shrubs  of  cold  countries  this 
transformation  of  starch  will  be  found  to  be  caused  normally  by  the 
changes,  probably  enzymatic,  that  follow  exposure  to  an  alternation 
of  high  and  low  temperatures  rather  than  exoosure  to  a  single  low 
temperature. 

(33)  DORMANl      PLANTS     MAKE     I  1 1 1  1 1:     EARLY      SPRING     TWIG     GROWTH     BEFOR]       M  \v 

ROO  is    BEGIN    TO    DE\  II  OP 

The  root  growth  of  blueberry  plants  in  early  spring  is  verv  slug- 
gish, in  strong  contrast  to  the  activity  of  their  stems.  In  the  plant 
illustrated  in  Plate  XIII.  figure  2,  no  new  root  growth  had  taken 
place  up  to  the  time  the  photograph  was  made.  For  their  early 
spring  growth  blueberry  plant-  seem  to  depend  on  the  food  stored  in 
their  twigs  the  year  before.  A  microscopical  examination  has  shown 
that  the  pith  and  medullary  rays  of  winter  twigs  are  gorged  with 
starch. 

It  may  he  of  interest  to  state  here.  a-  hearing  on  the  difficulty  of 
making  stem  growth  exhibited  by  an  improperly  wintered  blueberry, 
that  the  indoor  plant  shown  in  figure  1  of  Plates  XTI  and  XIII  had 
made  considerable  new  root  growth  at  the  stage  shown  in  Plate  XII 
and  abundant  root  growth  in  Plate  XIII.  The  starting  of  dormant 
buds  appears  from  this  and  many  other  similar  cases  not  to  be  influ- 
enced by  the  presence  or  absence  of  new  root  growth. 

A  practical  suggestion  based  on  the  late  spring  root  development  of 
the  blueberry  is  that  transplanting  may  perhaps  he  done  up  to  the 
time  of  flowering  with  little  injury  to  the  plant. 

(34)  I    M.Kss    POLLINATED   BY     \  N    OUTSIDE    AGENCY,    SUCH     \s    I\sii    I  >.    Mil     FLOWERS 

PRODUCE   LITTLE  OK    NO   FRUIT. 

Many  blueberry  plants,  from  seed  germinated  in  September.  L907. 
were  brought  into  flower  in  one  of  the  Department  greenhouses  dur- 
ing the  winter  of  L908  '•».  When  left  to  themselves  the  flowers  rarely 
produced  fruit.  The  greenhouse  contained  few  pollen-carrying  in- 
sects, a  few  ants  and  tlies  merely,  no  bees.  It  was  found  that  the 
flowers  were  so  constructed  as  to  he  unable  ordinarily  to  pollinate 
themselves.  The  lack  of  fruit  was  evidently  due  to  lack  of  pollina 
tion.     When  pollinated  artificially  the  flowers  usually  produced  fruit. 

In  its  natural  position  the  flower  (fig.  27)  is  not  erect  hut  in- 
verted, the  narrow  orifice  of  the  corolla  being  lowermost,  the  nectar 
welling  up  from  the  surface  of  the  disk  between  the  base  of  tin  style 
ami  the  base  of  the  filaments.  The  ten  stamens  and  the  style  hang 
downward  within  the  corolla,  the  stp.mens  being  shorter  than  the 
style.  The  pollen  when  mature  drops  down  from  the  two  anther 
sacs  through  the  two  anther  tubes  which  the  stamens  of  these  plants 
possess  and  out  at  the  terminal  pores.  'See  fig.  28.) 
193 


13,  Bureau  of  Plant  Industry,  U    S    Dept.  of  Agi 


Plate  XII. 


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Bui.  193,  Bureau  of  Plant  Industry,  U.  S.  Dup: 


Plate  XIII. 


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POLLINATION    OF    THE    BLUEBEKRN     FLOWER. 


77 


Fig.  27.     Flowers  of  tin'  blueberry,   from    1908  s I 

lin^s  of  the  lai  ed    Nen    Hampshire  bush  of 

I  <i.  i  in  mm  corymbosum :  n.  Flower  of  the  corym- 
bosum type  of  planl  :  h.  Bower  of  the  amocnum  type 
of  plant  ;  c,  same  as  '<.  bul  pari  of  the  corolla  re 
moved  to  show  the  stamens,  style,  and  stigma. 
i  Enlarged  •"•  diameters,  i 


The  operation  ol  the  mechanism  for  releasing  the  pollen  ma\  he 
observed  with  a  high-power  hand  lens.  The  stamens  hang  in  a  close 
circle  about  the  style.  The  filaments  are  broad  and  laced  into  a  tight 
tube  by  the  interweaving  of  their  marginal  hairs,  the  anther  sacs 
pre--  close  together,  and 
therefore  the  only  con- 
venient way  of  access  to 
the  nectar  is  through  the 
>lit-  between  the  anther 
uiIm's.  The  anther  tubes 
are  stiff  and  when  one  of 
them  is  pushed  to  one 
side  the  movement  is 
communicated  to  the  an- 
ther sac.  The  pollen  if 
mature  is  dislodged  and 
falls  dow  n  the  tube  and 
out  ;tt  the  orifice. 

The  pollen  does  not 
eonie  nut  of  the  anthers 
readily  on  a  cloudy,  humid  day.  but  on  a  warm,  sunny,  'Ivy  day  it 
accumulates  in  the  tubes  and  when  they  are  moved  it  run-  out  like 
grain  from  a  grain  chute.  The  pollen  grains  (fig.  29)  do  not  stick 
to  the  sides  of  the  parchment-like  anther  tube-  when  these  are  dry, 
but  they  have  the  faculty  of  adhering  to  hard  surfaces,  such  as  glass 

or  the  lend  of  a  lead  pencil,  and 
they  doubtless  would  adhere  also  to 
the  hard  -hell  of  an  insect  whether 
it  was  covered  with  hair-  or  not , 

The  pores  of  the  anther  tubes  do 
not  open  squarely  across  the  ends 
id'  the  tul»e-.  but  they  are  set  on  a 
long  bevel  facing  inward.  The 
pollen  when  released  would  there- 
fore fall  upon  the  stigma  were  it 
not  for  a  peculiarity  in  the  -true- 
lure  of  that  organ.  The  sticky 
stigmatic  surface,  which  the  pollen 
inu-t  reach  to  effect  pollination, 
is  at  the  apex  of  the  globular  or  top-shaped  stignia,  while  the  sides 
of  the  stigma  a-  far  up  a-  the  middle  have  a  '\vy  surface  ending  in  a 
-hoit  collar  a  little  wider,  during  the  curly  maturity  of  the  stigma, 
than  (he  widest  part  of  the  stigmatic  surface.  (See  fig.  30.)  In  the 
inverted    position  of  the  (lower  the   falling  pollen   strikes  tin-  dry 

193 


Fig.  28.     Stamens  of  1 1 1 . -  blueberry,  from 
Bower  shown  in  flg.  27,  <■ :  //.  View 
from    the    Inner    I  side    view. 

Both    views    show    the    broad    filament 
wiili    hairj     margins    and    the    anther 
i ubes,    and    pores.      i  Enlarged    ." 
diameters,  i 


78 


EXPERIMENTS    IN    BLUEBERRY     CULTURE. 


Fig.   29. — Compound  pollen  grain  of  the 

blueberry,    consisting    of    four  simple 

grains     permanently    cohering.  (En- 
larged 200  diameters,  i 


surface,  like  the  outside  of  an  inverted  funnel,  and  drops  off  the  rim 
or  remains  on  it,  without  reaching  the  stigmatic  surface  which  lies 
protected  beneath. 

Ordinarily  pollination  is  effected  by  some  insect  which,  pushing 
into  the  orifice  of  the  corolla  from  beneath  in  search  of  nectar,  releases 
the  pollen,  as  already  described.  In  continuing  its  quest  for  nectar 
the  insect  brushes  against  the  stigma  with  some  portion  of  its  body. 

which  is  covered  with  pollen,  either 
from  the  same  flower  or  from  some 
other  flower   previously   visited. 

In  pollinating  the  flowers  by 
hand  it  was  found  impracticable  to 
collect  sufficient  pollen  to  apply 
with  a  brush.  The  following  sim- 
ple and  convenient  method  of  pol- 
lination was  devised:  A  wide  opening  was  torn  in  a  corolla  with  a 
pair  of  forceps,  so  that  the  stamens  and  stigma  could  be  approached 
from  the  side.  Then  the  lead  of  a  lead  pencil,  flattened  on  one  side 
and  held  horizontally,  was  brought  up  against  the  open  end-  of  the 
anther  tubes  from  below.  A  portion  of  the  falling  pollen  was  caught 
en  the  flat  lead,  where  it  could  be  seen  easily  because  of  the  blackness 
of  the  background.  Pollination  was  then  completed  by  touching  the 
stigmatic  surface  gently  two  or 
three  times  with  the  pollen-laden 
lead.  A  pollinated  flower  may  be 
marked  readily  by  pinching  off 
with  forceps  one  or  more  of  the 
calyx  lobes.  Fruit  was  produced 
from  flowers  pollinated  either  with 
their  own  pollen  or  with  pollen 
from  another  flower. 

The  self-pollination  of  a  blue- 
berry flower,  without  insect  aid.  ap- 
pears to  occur,  but  only  occasion- 
ally. On  greenhouse  plants  fruit  fig 
is  rarely  produced  when  the  (lowers 
are  not  artificially  pollinated,  and 
the  same  is  true  of  outdoor  plants  protected  from  insects  by  a 
covering  of  gauze.  The  conditions  of  these  observations  were  not 
such  as  to  obviate  all  possibility  of  the  accidental  visit  of  some  insect, 
but  it  is  believed  that  real  self-pollination  occurred  in  some  cases. 

(35)    'I'm:   FRUIT   MATURES   ABOUT  TWO   months    Mill:    MM     FLOWERING. 

A  few  days  after  pollination  the  corolla,  with  the  stamens,  falls 
off.     The  stigma  al   this  time  has  turned  brown,  and  within  a  day  or 

u»:: 


.30. — IMstil  and  calyx  of  (lie  blue- 
berry,  showing  the  style  and  stigma. 
(Enlarged  .">  diameters.) 


Bui.  193,  Bureau  of  Plant  Industry,  U.  S.  Dcpt.  of  Agriculture. 


Plate  XIV. 


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RIPENING    OF    THE    I'IM'IT.  79 

two  the  style  also  falls.  The  calyx  remains  permanently  attached  to 
the  ovary  and  berry.  About  a  week  after  the  opening  of  tin-  corolla, 
the  "\  ary,  which  at  first  was  much  narrower  than  the  expanded  calyx, 
begins  to  swell  and  grow.  This  growth  continues  for  about  a  month, 
and  then  for  about  another  month  (lie  green  berry  make-  little  in 
crease  in  size.  A  few  day-  before  the  time  of  ripening  the  calyx 
turns  purplish,  nexl  the  green  color  of  the  berry  lake-  on  a  trans- 
lucent  appearance,  the  next  day  it  turns  to  a  light  purple,  and  the 
following  day  to  a  dark  purple  or  whatever  it-  permanent  color  may 
be.  During  these  leu  day-  die  berry  make-  a  very  rapid  growth,  its 
diameter  often  increasing  50  percent.  After  reaching  it-  permanent 
color  the  berry  changes  little  in  size,  but  for  several  days  continues 
to  improve  in  sweetness  and  flavor. 

It  i-  a  characteristic  of  blueberries,  important  from  the  standpoint 
of  picking,  thai  after  ripening  they  will  remain  on  the  hush  a  lon« 
time,  often  a  month  or  more,  without  losing  their  plumpness  or  their 
flavor.  This  make-  possible  the  removal  of  all  the  berries  fit  111  i 
bush  at  one  clean  picking,  unless  to  catch  a  fancy  market  a  partial 
early  picking  i-  desired. 

It  i-  of  intere-i  to  record  that  although  the  largest  berry  observed 
on  the  parent  bush  of  the  seedlings  of  September,  1907,  was  0.46  of 
an  inch  in  diameter,  a  berry  ripened  in  the  greenhouse  on  one  of  these 
seedlings  measured  on  April  2-1,  1909  (PI.  XV),  0.49  of  an  inch  in 
diameter,  and  August  2,  1909,  one  of  the  same  seedlings  had  a  ripe 
berry  <»..",  of  an  inch  in  diameter. 

(36)     So    FAR     \-    OBSERVED  THE    SWAMP    BLUEBERRY    WHEN    GROWN    IN     vein    soils    Is 
I  I  I  1  I  I     SUBJECT     TO  FUNGOUS  DISEASES  OR  INSEC1    PESTS. 

Like  all  plants  grown  in  greenhouses,  blueberry  seedlings  need  to 
he  watched  in  order  to  detect  and  -top  promptly  any  fungous  or 
insect    pest-  that    may  appear. 

With  the  exception  of  the  Asterocystis-like  root  fungus  described 
on  pane  65  a-  occurring  on  sickly  plant-  in  alkaline  soil-,  the  only 
parasitic  fungus  found  on  anv  of  the  plant-  was  a  mildew  identified 
by  Mrs.  flora  \Y.  Patterson  a-  Microsj)haera  alni  vaccina,  which  ap- 
peared sparingly  when  the  atmosphere  of  the  greenhouse  was  too 
moist.  This  mildew  is  abundant  on  Vaccinium  racillans,  hoth  wild 
and  cultivated,  hut  the  swamp  blueberry  i-  very  little  subject  to  it- 
attack-,  an  important  characteristic.  This  fungus  would  doubtless 
respond  readily  to  the  ordinary  treatment  for  mildew  with  pulverized 
sulphur. 

Amon-  insects  a  green  aphis  sometimes  threatened  to  damage  the 
growing  twigs,  but  it  was  easily  destroyed  by  tobacco  fumigation. 

The  greenhouse  red  spider  {Tetranychus  himaealatvs)  infested 
some  of  the  cultures,  e-pecially  in  the  warmer  greenhouses,  occurring 
chiefly  on  the  hack-  of  the  leaves,  an. I  seriously  injured  the  plants 

193 


80  EXPERIMENTS    IN     BLUEBERRY    CULTURE. 

unless  promptly  checked.  The  mosl  satisfactory  treatment  was  to 
syringe  the  plants  once  or  more  a  day  with  ;i  swift  spray  of  water, 
repeating  the  treatment  until  the  animals  were  cleared  off. 

A  pathological  condition  observed  in  the  summers  of  both  1908  and 
1909,  at  first  supposed  to  be  physiological  in  cause,  has  now  been 
traced  to  an  insect.  The  young  leaves  of  tender  shoots  become  .semi- 
transparent  or  "watery"  in  appearance,  remain  small,  develop  a 
faintly  rusty  color  on  the  lower  surface,  tend  to  become  slightly 
cockled,  and  sometimes  turn  brown  and  wither.  It  was  finally  ob- 
served that  these  leaves  were  infested  with  a  very  minute  animal, 
much  smaller  than  a  red  spider  and  when  not  in  motion  difficult  to 
distinguish  with  a  strong  hand  lens.  Specimens  submitted  to  Mr. 
Nathan  Banks,  of  the  Bureau  of  Entomology,  were  identified  by  him 
as  a  mite  of  the  genus  Tarsonemus  and  belonging  probably  to  an 
undescribed  species. 

A  similar  and  perhaps  identical  mite  had  done  considerable  dam- 
age to  young  seedlings  in  the  greenhouse  during  the  winter  of  1908-9, 
its  presence  being  indicated  by  the  conspicuous  cockling  of  the 
leaves.  The  difficulty  had  then  been  met  by  the  pruning  of  the 
affected  twigs.  It  was  observed,  however,  in  the  summer  of  1909 
that  the  mite  producing  the  watery  appearance  of  the  leaves  did  not 
occur  on  outdoor  plants  fully  exposed  to  rain  and  dew.  hut  only  on 
plants  partly  or  wholly  protected  by  glass.  It  is  suggested,  therefore, 
that  frequent  syringing  with  water  may  he  the  proper  mean-  to 
control  this  mite. 

On  the  whole,  this  species  of  blueberry  when  properly  grown  may 
be  regarded  as  unusually  free  from  the  depredations  of  fungi  and 
insects. 

IMPROVEMENT   AND   PROPAGATION. 
<?>7)  The  parent  plant  of  the  swamp  blueberry  seedlings,  the  culture  of 
WHICH     II  \s    been     described,    bore    berries    over     half    an    INCH     IN 

DIAMETEIi. 

The  parent  of  the  blueberry  seedlings  of  1908  was  a  hush  of 
Vaccinium  corymbosum  selected  at  Greenfield,  N.  H.,  in  July.  1908, 
after  three  summers  of  cursory  observation  in  the1  mountains  of 
southern  New  Hampshire  and  three  weeks  of  diligent  search  in 
the  summer  of  1908.  The  hush  grew  at  an  elevation  of  '.».■"><)  feet 
above  the  sea.  It  stood  with  many  other  blueberry  bushes  in  an 
old,  brushy,  mountain  pasture,  in  permanently  moist  hut  not  swampy 
soil.  It  was  about  7  feel  in  height,  and  the  largest  of  the  several 
stems  was  about  2  inches  in  diameter.  The  plant  was  old  and  sonic 
what  decrepit,  the  tops  on  some  of  the  stems  being  partially  dead. 
Some  parts  of  the  bush,  however,  were  in  full  vigor,  with  robusl 
foliage  and  twi^s.  The  leaves  were  dark  green  above  and  pale 
glaucous  green  beneath,  with  entire  margins,  and  smooth  on  both 
Bides  except  for  a  slight  pubescence  on  the  midrib  and  principal 
103 


Bui.  193,  Bureau  o'   i  .    U    S   Depr 


Plate  XV. 


Berry  Ripened  on  a  Blueberry  Seedling  at  the  Age  of  Nineteen  Months. 


A    I.  \i:i.i    BERRIED    BUSH.  81 

veins  of  the  upper  surface.  They  were  of  large  size,  on  the  fruiting 
twigs  reaching  ;i  length  of  2  inches  and  ;i  breadth  of  1  inch  and  on 
vigorous  shoots  having  the  corresponding  measurements  ■_'..">  and  1.5 
inches.  The  character  of  the  leaves  is  mentioned  in  detail  because 
of  the  remarkable  variation  shown  in  the  leaves  of  the  seedlings, 
particularly  in  size,  toothing,  color,  and  pubescence.  The  large 
flowers  produced  in  the  spring  of  L909  were  0.4  of  an  inch  (10  nun.) 
long  from  the  base  of  the  ovary  to  the  tip  of  the  corolla;  the  sepals 
were  very  short,  and  the  corolla  white  and  nearly  cylindrical. 

The  berries  were  of  large  size,  reaching  a  diameter  of  over  half 

an  inch.  The  color  was  an  unusually  pale  blue,  due  to  a  dense 
bloom  or  glaucousness  over  the  nearly  black  surface.  In  form  the 
berrj  Wits  nol  spherical,  but  somewhat  depressed  or  tomato  shaped. 
The  calyx  in  the  ripe  berry  (Pi.  VI,  fig.  L)  was  almost  obliterated, 
because  it  was  small  in  the  beginning  and  because  of  lateral  stretch- 
ing of  the  berry  in  acquiring  its  depressed  form.  This  smallness  of 
cal\  \  is  of  importance,  because  in  such  a  berry  no  shelter  is  afforded 
beneath  the  sepals  for  insects,  and  also  because  the  amount  of  "  rag," 
or  indigestible  skin,  is  much  less  than  in  a  berry  with  a  large  calyx. 
In  Savor  the  berry  was  exceptionally  good.  It  was  sufficiently  acid 
to  be  decidedly  superior  to  the  mild,  sweel  berry  of  Vaecinium  pt  nn- 
sylvani&um,  ye1  nol  sour  like  the  berry  of  V.  canadense.  It  repre- 
sent- one  of  the  best  types  of  flavor  in  the  variable  V.  corymbosum. 
The  only  unfavorable  feature  of  this  bush  was  the  lateness  in 
the  maturity  of  it>  berries,  a  characteristic  of  the  species  to  which 
it  belongs.  The  earliest  New  England  berries,  which  bring  the  fancy 
whole-ale  price  of  •_'()  cent-  or  more  per  quart  for  the  first  few  days, 
as  described  on  page  L2,  are  those  of  the  dwarf  Vacciniufn  penn- 
sijl I'unh  nm.  which  mature  about  two  week-  earlier  than  those  id' 
1'.  cori/mhiisuii). 

The  size  of  the  berry  is  of  such  importance  as  to  warrant  an  exact 
re  "id  of  the  measurement,  not  only  of  the  largest  berries  bul  of  all 
the  berries  from  an  average  picking.  On  A.ugus1  ■_'.  L908,  an  average 
pint  of  berries  was  taken  out  id'  a  clean  picking  of  this  bush  and  each 
heri'v  was  measured.  The  measuring  was  done  by  means  of  a  metal 
plate  containing  a  -eric-  of  circular  hole-  5,  6,  7  mm.,  etc..  in  diam- 
eter.    The  pint  of  berries  showed  the  following  sizes: 

l»inni«'(rr  of  berry.  Number  of  berries. 

7  to     s  mm    2 

8  I-    9  mm  50 

9  I"    L0   Him     1!il 

1 11   in  in                                                                      278 

11  to  12  mm  i:;7 

1-  t"  t:'.  inm                                            .    10 

13  I"   1  I   mm   

U71 
.MTiis       Bull,  fa::     H»        6 


82  EXPERIMENTS  IN  BLUEBERRY  CULTURE. 

The  largest  berry  measured  on  this  bush  was  14.02  mm.  (0.552  of  an 
inch)  in  diameter. 

Three  quarts  of  berries  were  picked  from  the  bush;  all  those  less 
than  10  mm.  in  diameter  were  discarded,  and  the  remainder,  about  2 
quarts,  were  carried  to  "Washington  for  seed  purposes. 

(38)  There  is  every  reason  to  believe  that  thk  blueberry  can  be  improved 
by  breeding  and  by  selection. 

The  swamp  blueberry  (Vaccinium  corymbosum)  is  an  exceedingly 
variable  bush.  There  are  three  especially  well-marked  forms,  called 
T.  amoenum,  V.  atrococcum,  and  I*.  pallidum,  by  some  authors 
regarded  as  distinct  species,  by  others  as  forms  of  I'.  corymbosum. 
Within  the  limits  of  these  forms  variation  is  also  extensive.  There  i^ 
great  opportunity  for  selection  among  wild  varieties  in  the  size,  color, 
flavor,  and  time  of  ripening  of  the  berries  and  in  the  productiveness 
and  vigor  of  the  bushes. 

That  types  possessing  desirable  qualities  can  be  crossed  there  is  no 
question.  A  method  of  pollination  has  already  been  described  (see 
p.  78),  which,  supplemented  by  the  removal  of  the  stamens  on  the 
female  parent  before  they  have  matured  their  pollen  and  also  by  the 
protection  of  the  pollinated  flowers  from  insects,  would  insure  a 
genuine  cross. 

The  possibility  of  securing  valuable  varieties  is  accentuated  by  the 
marked  variation  observed  in  the  character  of  the  offspring  of  the 
large-berried  bush  from  which  the  seedlings  of  1908  were  grown.  Be- 
sides minor  variations,  these  seedlings  show  three  forms  which  may 
be  regarded  as  types.  One  of  these,  characterized  by  its  low  stature 
and  leaves  tending  to  be  conduplicate  and  by  it-  long  persistence  into 
the  winter  in  a  green  state,  is  perhaps  the  result  of  some  pathological 
difficulty.  Two  of  the  types,  however,  appear  in  every  way  to  be 
normal.  One  has  its  leaves  huge,  obovate-elliptical,  glaucous  on  the 
back,  and  with  entire  margins,  such  as  are  possessed  by  the  parent, 
and  are  typical  of  true  Vaccinium  corymbosum,  and  it  develops  only 
a  few  though  very  robust  steins,  with  few  flowering  buds.  The  other 
has  smaller,  narrower  leaves,  green  on  both  surfaces,  and  with  mar- 
gins closely  and  evenly  serrulate.  It  produces  many  stems  smaller 
than  those  of  the  other,  and  more  numerous  flowering  buds.  It  is 
strongly  suggestive  of  the  plant  called  Vaccinium  <n/t<><  num.  It  is 
much  larger  and  more  robust  than  I'.  pennsylvanicum,  and  may  pos- 
sibly be  a  hybrid  between  that  species  and  I'.  corymbosum,. 

The  characters  of  bush  and  foliage  in  these  two  types  have  not  yet 
been  correlated  with  any  differences  they  may  show  in  (lower  and 
fruit.  It  is,  however,  of  great  interest  that  these  same  two  types 
occur  among  the  seedlings  of  1907,  as  well  a-  those  of  L908,  which 
'.line   from  a  different   though  similar  bush  growing  about  2  miles 

IV the  other. 

L93 


Ml   rHODS   OF    PROPAGATION.  83 

(39)    'Till     SWAMP  BL1  S    PROPAGATED  in    GRAFTING,    B1     BUDDING,  BY 

I    \\  I  IMNc.    B1      rWIG    il    [TINGS,     \\l>    BY     BOOT    M    [TINGS. 

On  March  2,  1909,  a  few  scions  of  the  large  berried  bush  from  NVu 
Hampshire,  dormanl  winter  twigs,  were  grafted  on  seedlings  of  L907 
which  had  been  started  into  growth  in  the  greenhouse.  The  actual 
work  of  grafting  was  done  by  Mr.  Edward  Goucher.  All  were 
simple  splice  grafts,  the  diagonal  cut  being  about  0.75  of  an  inch  in 
length,  the  diameter  of  stock  and  scion  at  the  point  of  contact  about 
0.15  of  an  inch,  and  the  length  <>f  the  scion  about  2.5  inches  after  it 
was  cul  off  at  the  tip  just  below  the  lowest  flowering  bud.  The 
splice  was  wrapped  tightly  and  completely  with  raffia,  but  no  wax  was 
applied  except  to  the  cul  tip  of  the  scion.  In  order  t<>  prevent  a  pos- 
sible injurious  degree  of  evaporation  from  the  scion,  the  whole  graft, 
which  was  near  the  base  of  the  plant,  was  surrounded  nearly  to  the 
tip  of  the  scion  with  a  loose  mass  of  sphagnum,  which  was  kept 
slightly  moist  though  well  aerated. 

A.11  the  scions  put  out  new  growth  from  their  buds  in  about  ten  days. 
In  hall'  the  grafts  union  did  not  take  place,  the  new  growth  finally 
collapsed,  and  the  scion  died.  In  the  others  the  surfaces  united 
satisfactorily  and  the  wrapping  was  removed.  By  the  end  of  the 
season  of  1909  the  grafts  had  made  a  growth  of  •">  to  8  inches  and 
had  laid  down  flowering  buds.      (See  PI.  XVI,  6g.   1.) 

The  first  experiments  in  budding  were  begun  on  August  13,  L909, 
tin-  work  being  done  by  Mr.  Henry  II.  Boyle.  Seven  seedlings  of 
L906  and  1907  were  budded  with  summer  leaf  buds  of  the  large- 
berried  Vaccinium  corymbosum  bush  from  New  Hampshire.  On 
A.ugust  16,  6  other  seedlings  of  L906  and  L907  were  budded  with  buds 
from  large-berried  plants  of  V.  pallidum  from  North  Carolina.  On 
September  ■_'  and  :'>.  1909,  26  more  seedlings,  of  1907  and  1908,  were 
budded  with  hud-  from  the  New  Hampshire  hush.  The  buds  were 
inserted  near  the  base  of  the  plan!  on  stems  0.25  to  0.5  of  an  inch  in 
diameter.  The  method  of  procedure  was  that  used  in  ordinary  hud 
ding,  as  of  peaches,  the  same  T-shaped  cut  being  made  in  the  hark  of 
the  -lock,  the  hud  wood  cut  to  the  length  of  half  an  inch  or  a  little 
more,  and  the  bud  after  insertion  wrapped  tightly  with   raffia. 

The  percentage  of  success  in  the  budding  was  small.  Out  of  the  39 
plant-  budded  only  L6  retained  their  hud  alive  and  in  apparently 
good  condition  at  the  end  of  the  season,  and  the  following  spring 
only  5  were  alive  and  in  condition  to  grow.  Plate  XVI,  figure  2, 
is  a  reproduction  of  a  photograph  of  one  of  the  successful  buds  from 
the  large  berried  New  Hampshire  bush,  taken  in  the  winter  of  L909 
L0  after  union  had  taken  place,  the  wrapping  had  heeii  removed,  and 
the  stock   hail   heen  cut   nil    ;iImi\  e  the  hud. 

iments  on  some  of  the  feature-  of  these  budding  experiments 
may   he  useful   i"  other  experimenters.     Tie-  growth   of  the  stems 

I'..:; 


S4  EXPERIMENTS    IX     BLUEBERRY    CULTURE. 

during  the  portion  of  the  season  remaining  after  the  budding  was 
sufficient  to  strain  the  wrappings  and,  unless  the  bud  wood  was  held 
tightly  for  its  whole  length,  to  push  the  hud  out  of  place.  It  was 
found  best  to  leave  the  bud  tightly  wrapped  to  the  end  of  the  season, 
notwithstanding  the  fact  that  the  stock  might  become  deeply  creased 
and  choked. 

An  examination  of  the  buds  that  failed  showed  that  in  mosl  cases 
baik  or  callus  from  the  stock  had  intruded  between  the  stock  wood 
and  the  bud  wood,  sometimes  covering  the  entire  surface.  While 
the  bud  wood  in  some  such  cases  was  in  part  still  alive  and  green,  it 
was  of  course  doomed. 

As  late  as  August  30  in  New  Hampshire,  and  September  3  in 
Massachusetts,  bushes  of  the  swamp  blueberry  were  found  in  which  the 
baik  would  peel  and  buds  could  be  inserted.  On  September  2  no  wild 
bushes  of  Vaccinium  atrococcum  could  be  found  at  Washington  in 
condition  to  bud.  Even  in  Massachusetts  and  New  Hampshire,  on 
the  dates  mentioned,  most  of  the  bark  on  all  the  bushes  and  all  of  it 
on  many  bushes  would  not  peel.  Bark  still  in  good  condition  oc- 
curred mostly  on  vigorous  shoots  of  the  season  and  in  some  cases  of 
the  preceding  season.  Sometimes  the  bark  on  the  north  side  of  an 
erect  shoot  would  peel  when  that  on  the  south  side  would  not.  Bark 
still  green  and  whole  would  peel  when  near-by  bark  which  from  age 
and  exposure  had  begun  to  turn  brown  and  split  on  the  surface  would 
not  peel. 

Propagation  by  layering  was  carried  on  in  1908  and  L909.  In 
the  greenhouse  experiments  moist  live  sphagnum  proved  to  be  a  more 
successful  material  than  peat  and  sand  in  which  to  root  a  layered 
branch.  When  the  branch  laid  down  was  one  which  was  hardening 
its  wood  but  still  bearing  leaves,  it  callused  and  rooted  readily  in  the 
sphagnum  at  the  point  where  the  bark  was  sliced,  but  when  a  young 
soft-wooded  branch  was  used  it  usually  began  to  decay  at  the  cut 
and  finally  died.  Although  several  times  tried  it  was  never  found 
practicable  to  sever  a  layered  and  rooted  branch  from  the  parent 
plant  successfully  except  at  the  period  of  winter  dormancy  after  the 
leaves  had  been  shed. 

(40)     Tin:    Mosl    DESIRABLE    METHOD   OF   PROPAGATING    THE   SWAMP   ni.rEBERHY    IS   BY 
t  UTTINGS. 

While  the  surest  method  of  propagating  a  selected  blueberry  bush 
is  by  layering,  and  the  most  rapid  method  of  securing  fruiting  plants 
from  it  is  by  grafting,  both  these  methods  have  certain  objections 
which  do  not  apply  to  the  method  of  propagation  by  cuttings. 

Propagation  by  grafting  is  objectionable  because  of  the  habit  the 
blueberry  plant  has  of  continually  sending  up  new  -hoot-  to  replace 
(he  old  stems.     These  shoots  come  from  the  root  or  from  the  base,  of 

193 


Bui.  193,  Bureau  of  Plant  Industry,  U.  S.  Dept.  of  Agriculture. 


Plate  XVI 


Fig.  1. -Grafted  Blueberry. 


Fig.  2.— Blueberry  Seedling  Successfully 
Budded. 

The  line  of  union  between  the  .stock  and  the  scion  in  figure  1  is  clearly  shown.    Two  twigs  had 

grown  from  the  scion,  a  short  one  near  the  tip  and  a  vigorous  one  from  the  lower  part.     In  ligure 

shown  an  inserted  i>u<1  which  has  united  y  with  the  stock,  bu I  has  not  yel  begun 

to  grow.    The  insel  atural  size.    The  two  va  arc  natural 


PROPAG  \  I  i"N    \:\    CI    CTING 

the  stem  jusl  below  the  surface  of  the  ground.  Originating  below 
the  graft  they  would  not  bear  fruit  of  the  variety  desired,  and  such 
a  grafted  plant  would  always  be  liable  to  serious  depreciation  in 
value.  It  is  suggested,  however,  for  the  benefit  of  any  who  may 
de-ire  to  follow  up  this  method  of  propagation,  that  a  plant  produced 
l>\  root  grafting  would  be  somewhal  less  liable  than  a  stem  graft  to 
i  he  product  ion  of  -hoot-  from  the  stock. 

Propagation  by  layering  i-  not  open  to  the  objection  just  raised 
against  propagation  by  grafting.  The  difficulty  with  layering  is 
that  only  a  few  plant-  can  be  propagated  from  a  parent  in  l\\\>  way 
at  one  time.  The  method  of  layering  i-  slow  and  therefore,  from  a 
commercial  point  of  view .  faulty. 

Propagat  ion  by  cuttings,  whether  of  the  root  or  the  stem,  is  subject 
in  neither  of  the  objections  raised  to  grafting  and  to  layering.  In 
a  plant  raised  from  a  cutting  the  whole  plant  body,  including  the 
root,  is  of  the  variety  desired,  and  alien  -hoot-  can  never  be  pro- 
duced. Furthermore,  hundreds  or  even  thousands  of  cuttings  may 
be  taken  at  one  time  from  a  valuable  plant  and  a  large  stock  of  off- 
spring .-an  -nun  be  accumulated. 

The  present  objection  to  the  propagation  of  the  swamp  blueberry 
by  cuttings  i-  the  difficulty  of  making  a  high  percentage  of  the  cut- 
tings "Tow.  In  this  respect  the  experience  of  the  last  two  year-  may 
he  characterized  a-  a  series  of  frequent  alternations  of  high  hopes  and 
disappointing  failure-.  The  intimate  knowledge,  however,  acquired 
from  these  experiment-  regarding  the  behavior  of  cuttings  under 
many  different  condition-  gives  ground  for  confidence  in  ultimate 
success;  hut  a-  we  are  only  in  the  middle  of  things  in  this  matter  a 
full  description  of  the  experiments  with  cuttings  must  be  deferred 
until  satisfactory  results  shall  confirm  our  confidence  in  the  methods 
used. 

For  the  present  it  may  suffice  to  show  an  illustration  of  a  plant  from 
a  root  cutting  (fig.  31)  and  another  of  plant-  from  twig  cuttings 
(  PI.  XVI 1  |  of  the  big  berried  bush  from  Greenfield,  N.  II.  In  Plate 
Will  i-  illustrated,  from  a  photograph  taken  in  the  winter  of  L909  10, 
a  plant  grown  from  a  cutting  taken  on  October  L5,  1908,  from  a 
line'  of  September.  1907.  Although  itself  only  a  year  old,  and  even 
then  taken  from  a  seedling  only  a  year  old.  the  plant  after  passing 
the  winter  of  1908  '-1  in  the  greenhouse  and  the  summer  of  L909  out 
door-,  had  laid  down  156  flowering  hud-  at  the  time  it  wa-  photo- 
graphed. 

While  these  cases  -how   that  swamp  blueberry  plant-  can  he  pro- 
duced successfully  from  root  cuttings  and  stem  cuttings,  the  suce 
have  been  so  erratically  distributed  that  the  recommendation  of  any 
particular  method  i-  hardly  warranted  at  the  present  time. 


86 


l  Al'l  i;i.\i  KX'is   in    BLUEBERRY   CULI  i  ! ;  I . . 


It  should  be  stated  here  that  those  species  of  blueberry  which 
spread  by  rootstocks,  such  as  V actinium  pennsylvanicum,  and  other 
related  plants  having  the  same  habit,  like  the  deerberry  (Polycodium 
stamineum)  and  the  dwarf  huckleberry  (Gaylussacia  dumosa),  have 


Fig.  31. — Blueberry  plan!  grown  from  :i  rool  cutting.     (Natural  size.) 

been  reproduced  without  difficulty  by  rootstock  cuttings.  This 
method  is  not  generally  applicable  to  the  swamp  blueberry,  however, 
as  large  plants  of  (his  species  seldom  produce  rootstocks. 

FIELD    CULTURE. 

i  II  i    Experiments  ii  we  keen  begun  in  the  field  culture  of  thi   sw  smc  blue- 
berry. 

While  the  results  of  the  pot  culture  experiments  arc  regarded 
as  highly  successful  and  satisfactory,  the  experimental  field  plant- 
ings made  in  1908  and  1909  can  not  be  said  to  have  given  more  than 

193 


Bui.  193.  Bu'.  .    U.  S   Dept 


Plate  XVII. 


FIELD  PLANTINGS.  8*3 

promising  results.  Ii  is  true  that  out  of  one  planting  of  L79  seed- 
lings of  l!K)7  made  in  ;i  partially  moist  natural  meadow  at  Green- 
Geld,  N.  II..  in  early  July,  L908,  97  per  cent  outlived  the  severe 
drought  of  that  summer  and  the  rigors  of  the  following  winter, 
ami  6  percent  flowered  and  set  fruit.  The  plant-  were  not  observed 
during  the  ripening  season.  While  this  record  of  flowering  and 
fruiting  in  plant-  2  year-  of  age  may  be  regarded  as  satisfactory 
in  comparison  with  the  several  year-  supposed  by  the  earlier  experi- 
menters to  be  required  before  fruiting,  it  nevertheless  can  not  be 
regarded  as  satisfactory  in  comparison  with  the  pot  cultures  from 
the  seedlings  of  l'.'i>s.  of  which,  as  stated  on  page  73,  To  per  cent 
were  prepared  to  flower  in  1910,  their  second  year. 

While  the  results  of  the  field  experiment-  thus   far  made  are  re 
garded  as  in  no  wise  approaching  what  may  confidently  and  reason- 
ably be  expected,  they  nevertheless  may  serve  even  at  this  early  stage 
to  eon\ ey  some  useful  lessons. 

The  held  planting  of  L79  plant-  already  referred  to  contained 
sl  plants  which  had  never  been  potted  but  were  torn  apart  out 
of  their  original  seed  flat  while  in  full  growth  and  set  outdoors  in 
the  place  indicated.  These  plant-  after  such  severe  treatment  never 
grew  to  be  robusl  and  none  of  them  flowered.  It  was  among  them 
that  all  but  two  of  the  deaths  in  the  field  occurred.  That  any  of 
the  plant-  should  survive  such  rough  usage  is  of  interesl  experi- 
mentally, but  in  actual  practice  such  a  method  should  never  of  course 
be  followed. 

Most  of  the  field  plantings  were  made  in  area-  where  the  natural 
soil  hail  been  chopped  with  a  mattock  to  the  diameter  of  about  18 
inches  and  the  depth  of  about  8  inches  immediately  before  the  plant- 
ing. Ii  i-  evident  from  the  comparison  of  certain  plantings  made 
in  L909  thai  a  growing  plant  when  set  out  in  such  freshly  chopped 
soil  receives  a  serious  setback.  On  dune  I.  1909,  216  seedlings  of 
I'.'iis  were  set  out  in  new  hole-  prepared  as  described  above,  and  is 
other  seedlings  of  puis  were  used  at  the  same  time  to  replace  dead 
or  feeble  plant-  set  out  in  the  preceding  year.  These  Is  plant-  there- 
loir  went  into  soil  thai  had  rotted  for  a  year,  although  it  was  in 
part  penetrated  again  by  new  roots  from  the  surrounding  native 
vegetation.  When  nexl  examined,  on  dune  30,  the  two  groups  of 
plant-  showed  the  mosl  marked  difference  in  growth.  The  plants 
in  the  new  hole-  showed  the  same  purpling  of  the  leaves  and  cessa- 
tion of  growth  as  did  plant-  in  the  greenhouse  when  suffering  from 
excessive   acidity    due    to    potting    in    raw     peat.      (See    p.    60.)       The 

plant-  in  the  old  hole-,  on  the  contrary,  were  nearly  all  of  g 1  color 

and  growing  well.  It  i-  inferred  from  this  observation  that  blue- 
berry plants  will  do  better  if  the  holes  in  which  they  are  -et   are 

193 


88  EXPERIMENTS  IN  BLUEBERRY  CULTURE. 

filled   with    peat    or   peat    mixture   the   acidity   of   which   has   been 
tempered  by  several  months  of  decomposition. 

In  all  the  field  plantings  thus  far  made  the  plants  were  set  out 
while  in  full  growth.  Although  most  of  them  were  in  pots  when 
transplanted,  and  therefore  carried  their  entire  root  system  with 
them,  nevertheless  it  is  regarded  as  highly  probable  that  a  better 
plan  would  be  to  set  the  plants  out  when  dormant,  in  the  early  spring 
of  their  second  year.  Such  a  plan  would  offer  several  advantages 
which  it  is  hardly  necessary  to  recount. 

For  several  days  after  transplanting,  the  plants  were  partially 
shaded.  Paper  and  the  branches  of  various  trees  and  bushes  were 
tried  for  this  purpose.  Pine  branches  stuck  in  the  ground  on  the 
south  side  of  the  plants  were  found  by  far  the  best  of  the  shades  used. 

The  soil  about  the  plants  was  mulched  in  most  cases  with  dead 
leaves,  held  in  place  when  necessary  by  a  little  earth  thrown  over 
them. 

CONCLUSION. 

In  conclusion,  to  those  desiring  to  experiment  with  the  field  culture 
of  the  swamp  blueberry,  whether  with  wild  plants,  seedlings,  or 
plants  grown  from  cuttings,  two  modes  of  treatment  are  suggested. 
both  deduced  from  the  experiments  already  made.  The  first  method, 
suited  to  upland  soils,  is  to  set  the  plants  in  trenches  or  separate 
holes  in  well-rotted  peat  at  least  a  foot  in  depth,  and  mulch  the  sur- 
face well  either  with  leaves  or  with  clean  sand.  The  excavations 
should  provide  ample  space  for  new"  growth  of  the  roots,  not  less 
than  a  foot  each  way  from  the  surface  of  the  old  root  ball.  The  peat 
used  may  be  of  either  the  bog  or  upland  type,  as  described  OB  pages 
32  to  35  of  this  publication,  and  should  have  been  rotted  for  several 
months  before  using.  The  soil  in  which  the  holes  or  trenches  are 
situated  should  be  such  as  to  provide  good  drainage,  the  ideal  condi- 
tion of  the  peat  about  the  roots  of  the  plant  being  one  of  continued 
moisture  during  the  growing  season,  but  with  all  the  five  water  drain- 
ing away  readily  so  that  thorough  aeration  of  the  mass  of  peal  i- 
assured.  If  the  surrounding  soil  is  sufficiently  porous  to  insure  the 
maintenance  of  such  a  moist  and  aerated  condition,  without  the  neces- 
sity of  mixing  sand  with  the  peat,  better  growth,  it  is  believed,  will 
be  secured  than  when  such  a  mixture  is  used. 

The  second  method  of  field  culture  suggested  is  to  set  out  the  plants 
in  a  peat  bog  after  the  bog  has  been  drained,  turfed,  and  deeply 
mulched  with  sand.  The  treatment  proposed  is  the  same  as  that 
employed  in  cranberry  culture,  except  that  no  special  provision  need 
be  made  for  rapid  Hooding  of  the  bog  for  winter.  The  ground  water 
in  the  bog  may  probably  he  kept  with  advantage  a  little  lower  than 
is  usual  with  cranberries.  This  method  of  culture  is  suggested  not 
193 


Bui.  I9: 


Plate  XVIII. 


_    -o 


%  i 


Al'Vh  r.    CO    BXPERIM  I  \  I  ERS.  89 

only  because  of  the  close  botanical  relationship  of  the  swamp  blue- 
berry and  the  cranberry  and  the  known  similarity  of  their  ph}rsiolog- 
ical  requirements  in  the  matter  of  peal  and  moisture,  as  well  as  the 
presence  of  a  mycorrhizal  fungus  in  the  roots  of  both,  but  also  and 
especially  because  the  mosi  robust  growth  in  all  the  pot  experiments 
occurred  when  the  roots  of  the  plant  were  feeding  on  pure  peat  and 
the  pots  were  surrounded  by  moisl  -and.  The  important  effects  of 
these  conditions  arc  discussed  on  pages  68  to  71.  Essenl ially  the  same 
effects,  it  is  believed,  are  secured  bj  the  system  of  culture  used  for  the 
cranberry. 

Tin-  publication  closes  with  no  special  summary  of  results.  The 
numbered  statements  which  form  ii-  framework  arc  in  themselves  a 
sufficient  summary  for  the  general  reader,  and  one  who  i-  led  by  these 
experiments  to  undertake  the  culture  of  the  blueberry  will  find  it 
profitable  not  to  begin  hi-  work  until  he  ha-  read  the  whole  of  the 
publication.  These  plants  differ  in  their  -oil  requirements  so  funda- 
mentally from  all  our  common  cultivated  crop-  that  it  i-  useless  to 
expect  to  succeed  with  their  culture  without  a  thorough  understand- 
ing id'  the  principles  governing  their  growth. 

Those  desiring  to  look  into  the  work  of  earlier  experimenters  can 
find  a  key  to  the  literature  in  F.  W.  Card"-  book  entitled  u  Bush 
Fruits,"  or  in  the  article  by  W.  M.  Munson  on  Vaccinium,  in  Bailey's 
Cyclopedia  of  American  Horticulture. 


1  NDE  X. 

i  itric,  norma]  solution,  relation  to  pure  lemon  juice 28 

nutrient  solution.    See  Solution,  nutrient 
il,  arid. 

Acidit) .  phenolphthalein  test 26  28 

,  peat,  i                    .  etc 22,  35,  'il  62 

Aeration,  conditions  satisfactory  for  blueberry 17,3"  39,55 

necessity  in  interior  of  pots 69 

promoted  l>y  plunging  potted  plants (i.">-(i7,  <;n 

\  ricultural  experiment  stations.     Sei  Stations,  agricultural  experiment. 

A  labama,  absence  of  blueberry  and  related  plants  in  "  black  belt" 19 

Alfalfa,  |>"t  cul lures  in  garden  soil  and  in  peat,  comparison 15   17 

preference  for  alkaline  soils 29 

darkening  of  glass  p                sarj  to  prevent  growth I"> 

Alkali,  determination  by  phenolphthalein  test 22, 26  28 

Alkaline  nutrient  solution.    Sei  Solution,  nutrient. 

-oil      Si  i  Soil,  alkaline 
Alpine  blui  bi  n  .      Sei  Blueberrj  .  alpine. 

Ammonia  <l»ri  \  ed  from  hum  us 17 

solution  used  to  extract  humus 17 

Andromeda  polifolia,  root  fungus,  study 49 

Aphi                  lestruction  by  tobacco  fumigation 79 

Arboretum                        I  ierry  bushes II 

Arbutus,  trailin                      of  limestone  soils 1!) 

bl  ii"  e  to  injurious  fungus  of  blueberry  root 65 

Atl.i;      C  I  I  Plain       So    Plain,  Atlantic  Coastal. 

Atmospheric  nitrogen      Sei  Nitrogen,  atmospheric 

nudi flora,  occurrem  e  in  bogs  and  on  sandy  uplands :5"> 

of  kaltnia  peat  for  growing :ii> 

Azotobacter  chroococcum,  nitrogen-fixing  bacterium  in  soil 49 

Bacteria,  in  clover  toots,  fixation  of  atmospheric  nitrogen 48   19 

kaltnia  peat  and  cow  manure,  comparison I 14 

nitrifying,  inability  to  thrive  in  acid  soil 46,47 

of  ordinary  leaf  decay,  conditions  of  inability  to  thrive 31  32 

Hanks,  Nathan,  identification  of  mite 80 

Hark,  condition  for  budding 84 

Branch  s,  basal. 
slio  -     Shoots,  basal 

"  Belt,  black,"  Alabama,  absence  of  blueberry  and  related  plants pi 

Berry,  size,  flavor,  etc.,  in  various  species 12 

importance  as  market  feature 12,  II 

on  parent  plan! 81,82 

I  i  uit. 

Belt,  black." 

Blackening,  leaves   a  pathological  disturbance 

Bladderwot  ipply  of  nitrogen o 

Bloodroot,  sod  not  suitable  for  blueberry 24 

Blueberries,  prices  in  market .  .'. 12.  si 

il  preferences pt 

and  hucklebi  of  distil  

related  plants,  occurrem  e,  adherence  to  ai  id  soils 

Sei   Bo     I'll.-  berry. 

branching  types,  description 

mse 

caustic  effect  of  lime  on  plants 

cockling  of  leaves  due  to  a  mite 

elusions,  Bummary,  statement. 

■  dons,  dest  ription  and  development  of  branches  from  axih 


193 


91 


92  EXPEBIMENTS  IN    BLUEBERRY  CULTURE. 

Page. 

Blueberry,  cultivation,  possibility,  erroneous  popular  idea 11 

cultural  features  contributing  to  rapid  growth 68-71 

flowers,  description 76-78 

growth,  peculiarities 14-50 

improvement  and  propagation 80-86 

insect  pests 79-80 

market  price  and  requirements 12,  81 

name  usually  restricted  to  plants  of  the  genus  Vaccinium 13 

nutrition,  peculiarities 40-50 

peculiarities  of  growth 14-50 

nutrition 40-50 

picking  methods 13 

possible  hybrid 82 

pot  culture,  methods 51-80 

roots,  epidermal  cells 42-44 

soil  deleterious  to  roses  and  alfalfa 15-17 

requirements 14-40 

subalpine,  soil  preferences 19 

swamp,  or  high  bush 11.  14 

theory  of  nutrition 50 

variability 82 

See  also  Berry,  Fruit,  Fruiting,  and  Market. 

Bog,  blueberry,  water  level 36,  38-39 

cranberry,  near  Wareham,  Mass.,  growth  of  blueberry 36 

leatherleaf,  typical,  growth  of  blueberry  in  drained  areas 35 

peat,  formation,  causes  of  acidity 31-32 

suitability  for  growing  blueberries 88-89 

plants.     See  Plants,  bog. 

sphagnum,  growth  of  cushions 39 

water.     Sn  Water,  bog.  and  Water,  peat. 

Boston,  price  of  blueberries  in  market 12,, 8] 

Boyle,  H.  H.,  budding  of  swamp  blueberry 83 

Bract,  formation  prior  to  termination  of  stem  growth 58 

Branches,  basal,  commencement,  location  and  importance 57-58 

pine,  use  as  shade  for  blueberry  plants 88 

Branching  types  of  blueberry.     See  Blueberry,  branching  types 

Breazeale,  J.  F.,  assistance  in  experiments 27, 32 

Breeding,  use  in  improvement  of  blueberries 82 

Briggs,  L.  J.,  test  of  kalmia  peat 38 

Britton,  Mrs.  N.  L.,  identification  of  moss  on  leaf  mold 30 

Brown,  G.  H.,  on  plants  in  Smithsonian  grounds 11 

Budding,  method  of  propagation  of  swamp  blueberry 83-84 


9. 


Buds,  changing  by  pruning,  experiment vz 

flowering,  method  of  production 67,  71-73 

leaf,  tr.in  form  ition  into  flowering  buds 71-73 

Calcareous  soil.      See  Soil,  calcareous. 

<  'aleiuni  bumate,  occurrence  in  soils 46-47 

oxid  in  leaf  mold,  amount 30 

Calyx,  coloration  before  ripening  of  berry 79 

relation  to  quality  of  berry 81 

Canada,  relation  of  blueberries  to  calcareous  soils 19 

( 'ape  heaths.      See  Heaths. 

t  iarbonate,  lime,  use  in  pot  cultures  of  blueberry 

(  aid,  I''.  \\\,  on  blueberry  cultivation 89 

Cells,  epidermal,  of  blueberry  rootlets,  microscopic  study 42 

Cellular  matter.     See  Matter,  cellular  and  organic. 
Centrifugal  method.    See  Soil,  moisture  measurement. 

Chamacdaphne  calyculata,  bog.  growth  of  blueberry 35 

Chlorophyll,  presence  essential  to  development  of  carbohydrates 48 

<  litric  acid.     Se<    \<id,  citric. 
Clay  soil.     See  Soil,  clay. 

Si  e  also  Loam,  claj  ey. 

I  lo  iridium  pasleurianum,  nitrogen-fixing  bacterium  in  soil 

Clover,  nitrogen  absorption  by  plant 48-49 

Coastal  Plain.    See  Plain,  Atlantic  Coastal. 
193 


[NDEX.  03 

Cobb,  N.  A.,  method  of  installing  microscope 12 

Cockling  "i  blueberry  leaves  due  to  a  mite 80 

Collin-.  ( i    V.  photographs  illustrating  peal  formation 33 

Color,  importance  as  market  feature 12 

ration      s     Purpling. 

Conclusions,  summary  statement 

Cotyledons      s"  Blueberry,  cotyledon 
nberrj  bog.     Set  Bog,  cranberry, 

culture  system,  adaptability  to  blueberry     rowing  6 

European,  rool  fungus,  study 19 

i  rocks,  broken,  use  in  soil  for  repotting  heath  plants 69  70 

( Irossing,  use  in  improvement  of  blueberry 82 

Cultivation,  blueberry,  possibility,  erroneous  popular  idea II 

Culture,  conclusions,  summary  statement 

field,  of  the  blueberry 

pot,  methods,  swamp  blueberry d   80 

water,  experiment 36 

Cushions,  sphagnum,  growth  in  peat  bogs :i!) 

Cuttings,  development  of  flowering  buds  on 73 

use  in  propagation,  advantages  and  objection 84  - 

Cypripedium  acaule,  occurrence  in  bogs  and  on  sandy  uplands 35 

Darkening  of  glass  pots,  method !•"> 

Dawson,  Jackson,  on  growth  of  blueberry LI,  68  69 

Dei  i  berrj .  propagation  by  rootstock  cuttings 

undergrow  th  on  noncalcareous  soils,  Alabama 19 

Dormunt  plants.     Set  Plants,  dormant. 

Douglass,  John,  partial  planting  of  Smithsonian  grounds II 

Downing,  A   .1  .  plan  oi  Smithsonian  grounds 11 

Drainage,  necessity  in  field  culture 88 

I'll  -  pots 14 

See  also  Watering. 

ra,  insect  t 1  for  supplj  of  nitrogen 50 

Dry ne.-~,  importance  as  market  feature 12 

physiological,  discussion 3."> 

soil,  injur}  to  blueberry  plants (ii>.  69 

Earthwi inns,  injurious  effects  on  bin. 'berry  plants 38 

I    i  itrophic  mycorrhiza.     Set  Mycorrhiza. 

Embryo,  blueberry  seed,  development 53 

Endosperm,  blueberry  seed 53 

Endotrophic  mycorrhiza      S      Mycorrhiza. 

matic  transformation.     v     Staj   h,  transformation. 
Epidermal  cells.    Si  i  Blueberrj ,  i 

ea  repens,  avoidance  of  limestone  soils 1!> 

Erica  spp.,  i  us,  study 49 

l  leaths  and  Heal  her, 
Experiment  station        :        !  itions,  agricultural  experiment. 

Extraction,  method  i'<  r  soil-acidity  tests '_'7 

Farklebernes,  undergrowth  on  noncalcai  ils,  Alabama L9 

ild,  M    I   ,  '  n      d  preferences  of  alpine  and  subalpine  plants in 

Ferns,  use  "t"  Man  land  peat  for  growing 32 

Field  culture.    Set    Culture,   field. 

for  seedlings 

Flavor,  excellence  in  parent  plant si 

importance  as  market  feature 12, 81 

Flax,  injurious  fungus  in  root 65 

Fl ling  of  blueberries  in  winter 

Flowering  bud-      Set  Buds. 

edlings 

Flowers,  description 7> 

Formulas,   acid   and  alkaline  nutrient   solutions 

Frank,  A    I!  ,  naming  of  fungus  endotrophic  mycorrhiza 43 

Freestone,  pieces,  use  in  soil  for  repotting  heath  plants 7<> 

Freezii  on  blueben     plants 

Fruit,  on  a  plant  eleven  months  old 


94  EXPERIMENTS   IN   BLUEBERRY  CULTURE. 

Page. 

Fruit,  pollination  necessary  for  production ' 76 

ripening  process,  description 78-79 

Si,  also  Berry. 

Fruiting  of  swamp  blueberry 68,81,87 

Fungi,  growth  < 'game  mailer  containing  no  nitrates 48 

m\  corrhizal,  study  by  Charlotte  Ternetz 49-50 

Fungus,  beneficial  in  rootlets 42-45,  48  50,  89 

injurious,  found  in  roots  of  feeble  blueberry  plants 64  65 

Garden  soil.     See  Soil,  garden. 

Gaylussacia  dumosa,  reproduction  by  root  stock  cuttings 86 

frondosa,  a  blue-fruited  huckleberry 13 

Germination  of  seeds 14,  51, 53 

(ilass  for  covering  s 1  flat,  advantages 52  53 

pots.     See  Pots,  "lass. 

Goucher,  Edward,  grafting  of  swamp  blueberry 83 

Grafting,  use  in  propagation S3.  M  No 

Greenfield,  N.  H.,  field  plantings  of  blueberries 80,  87 

Growth,  check    after    transplanting,  forms  and  causes 55-57 

large,  attained  in  pot  <  ulture 68  7 ! 

peculiarities,  in  the  blueberry  plant 14-50 

root,  miller  various  conditions 15, 17-21,23,  24,28,36,4  I.  57,66,  76 

spring,  in  blueberry  plants  after  wintering  outdoors 71   76 

stem,  termination 58-59 

twig,  under  various  conditions 70.  76 

vigorous  under  certain  cultural  methods 68  71 

Hairs,  root,  absence  from  blueberry 40-41,  50 

ordinary  agricultural  plants, description  and  function 40-41 

Hardiness  of  blueberry  plants,  winter  exposure 7  1  76 

Heather,  avoidance  of  limestone  soils 19 

n  ii  il   fungus,  study 49 

Heaths,  propagation,  cultivation  etc.,  citations  from  William  McNab 63,  69,  70 

Honeysuckle,  swamp,  occurrence  in  bogs  and  on  sandy  uplands 35 

Huckleberry  and  blueberry,  means  of  distinguishing 13 

avoidance  of  limestone  soils 19 

dwarf,  reproduction  by  rootstock  cuttings 8(> 

name  applied  in  New  England  to  genus  Gaylussacia 13 

Humate.     See  Calcium  humate  and  Magnesium  humate. 

Humification,  definition 47 

Hummocks  in  peat  bogs 36,  39,  40 

Humus,  definition,  source  of  nil  rales,  extraction 46-47 

Improvement  of  blueberry,  discussion  of  methods 80-86 

Indoor  plants.     See  Plants,  outdoor. 

Inoculation  with  the  mycorrhizal  fungus  not  necessary It 

I  ii  ects,  capture  by  bog  plants,  nitrogen  supply 50 

injurious  to  blueberry 79  80 

larvae,  hastening  decomposition  of  leaves 33 

making  tunnels  in  clay  soil 24 

pollen-carrying,  in  pollination  of  blueberry 7(1  78,82 

Introduction  to  bulletin 11   II 

Kalmia  latifolia,  avoidance  of  limestone  soils Ii' 

See  also  Laurel. 
peal .     See  Peat,  kalmia. 

Kellerman,  K.  I''.,  on  bacteria  content  of  peal  and  manure 64 

formulas  for  nutrient  solutions 28t29 

kalmia  peat,  nitrates  and  nitrification 46,47 

Kentucky  limestone  soil.     Se<  Soil,  Kentucky  limestone 
Klamath  Lake,  Lower.     Sir.  Lower  Klamath  Lake. 

Lady's-slipper,  occurrence  in  bogs  and  on  sandy  uplands 35 

Larva'.     S,  i    Insects,  lar\  a  . 

Laurel,  avoidance  of  limestone  soils 19 

leaf  deposits  in  formation  of  Maryland  peal :;-; 

rool  fungus  similar  to  blueberry  fungus 43,44 

Set  also  Kalmia. 

Layering,  method  of  propagation  of  swamp  blueberry 84-85 

Leal  buds.     Si  <  Buds,  leaf. 
mold.    See  Mold,  leaf. 

103 


INDEX.  95 

Leatherleaf  bog.    Set  Bog,  leatherli  il 

Leaves,  character  on  parenl  plant ^<>  Bl 

deposits  in  peal  formation,  description 

maple,  effecl  on  growth  of  blueberry -  l  25,  62 

oak.  aciditj  testa 

useful  in  formal  ion  of  kalmia  peat 34 

fully  rotted,  deleterious  to  blueberry  plants 21  25 

partly  rotted,  suited  for  blueberry  soil 24,34 

purpling,  description  and  cause 

occurrence  and  pre>  ention 17,  25, 28, 29,  60  61,  87 

edling,  size  and  shape >4 

uppermost,  withering  and  stagnation,  causes 55  51 

water}  appearance  caused  by  mite 

n .  yields  nearly  normal  solul  ion  of  citric  acid 28 

Lime,  injurious  effects  on  blueberry 20,  23,  6 1  65 

■I  blueberrj  experiments 14,20  23,47,64  65 

Limed  soil.    Set  Soil,  limed 
Limestone  soil      Set  Soil,  calcareous. 

Limewater,  experiments  in  pot  cultures  of  blueberry 21  22 

Litter,  forest,  abundance  of  fungi  present 18 

i  layey,  mixture  with  sand  and  leaf  mold,  use  in  pot  cultures 25 

in  pol  cultures 14,25,52,54,60 

Klamath  Lake,  peat  with  alkaline  reaction 32 

McNab,  William,  on  culture  of  heaths 63,69,  70 

Magnesium  humate,  occurrence  in  soils 16   17 

Maine,  blueberries  in  Boston  market 12 

experiments  in  blueberrj  culture II 

Manure,  cow,  use  in  growing  plants 1  I,  63 

injurious  effect  on  blueberry L8  19,  64 

use  in  growing  heaths  and  blueberry 62  I  I 

w .Her.  use  in  growing  blueberry I 

Maple  [eaves.    Set  Leaves,  maple,  and  Woods,  sugar-maple. 
Market  requirements.     Set  Blueberry,  market  price  and  requirements. 
Marsh  rosemary.    Set  Rosemary,  marsh. 
Maryland  peal      Set  Peat,  kalmia. 

huaetts,  blueberries,  growth  in  cranberry  bog 36 

in  Boston  market L2 

Matter,  cellular  and  organic,  definitions 46 

Medullary  rays.    Set  Rays,  medullary. 

Michigan,  experiments  in  blueberry  culture II 

muck  lands,  loss  of  acidity  alter  drainage 

Mi  ■    cope,  use  iu  studying  blueberry  rootlets \l 

phaera  alni  vaccinii,  mildew  injurious  to  blueberry 79 

Mddeu  .  injurious  to  blueberry,  identification 79 

Mite  in              he  blueberry 80 

Mixtures,  soil,  used  in  pot  cultures 25,52     i.  >9  I  ! 

Mohr,  I  harles,  on  Uabama  soils 19 

Moisture,  absorption,  low  rate  in  bog  plants 50 

equivalent.     Set  Soil,  moisture  measurement. 

freed from  outside,  importance  as  market  feature 12 

measurement.     Set  Soil,  moisture  measurement. 

requirements  of  seed  flats 52 

Set  also  Watering. 

Mold,  leaf,  cause  of  alkalinity 35 

Eter  long  decomposition 24,35 

not  suited  to  the  blueberry 24  26 

proper  application  of  name 34 

ion  In  leal  lit  I er 34 

Moss,  Physcomitrium  immersum,  occurrence  on  alkaline  leaf  mold 30 

num.  aeration  conditions  satisfact  tj  for  blueberrj    

in  blueberrj  culture..... ." 39   10 

Muck,  loss  of  acidity  after  drainage 35 

Mulch,  leaves  or  -and.  for  field  plantings B8 

moist  leaf,  effei  I  on  growth  of  blueberry 24 

.   sufficient  winter  cover  for  blueberry  plants.   71 

!.  for  plunged  pots 68 

193 


9G  EXPERIMENTS  IN  BLUEBERRY  CULTURE. 

Page. 

Munson,  W.  M.,  on  blueberry  cultivation 89 

Mycorrhiza  in  blueberry  rootlets,  description  and  effects 42-45,  48-50,  89 

ectotrophic 43-44 

Myriapods,  hastening  decomposition  of  leaves 33 

Nectar  of  the  blueberry 76,  78 

Neutral  soil.     See  Soil,  neutral. 

New  Brunswick,  blueberries  in  Boston  market 12 

England,  occurrence  of  blueberry  and  related  plants 30 

Hampshire,  blueberry  shipments,  prices  received 12 

Jersey,  blueberries  in  Boston  market 12 

York,  absence  of  blueberry  and  related  plants  in  limestone  soils 19 

blueberries  in  Boston  market 12 

experiments  in  blueberry  culture 11 

Nitrates,  deficiency  in  peaty  soils I V  50 

determination  in  kalmia  peat 46 

usually  derived  from  humus 47 

Nitrification,  action  of  bacteria,  nonoccurrence  in  acid  forest  litter 47,  48 

Nitrifying  bacteria.     See  Bacteria,  nitrifying. 

Nitrites,  production 47 

Nitrogen,  absorption  from  soil  in  form  of  nitrates 45 

atmospheric,  fixation,  by  bacteria 48-49 

leguminous  plants 48-49 

root  fungi 48-50 

available,  deficiency  in  peaty  soil  due  to  lack  of  nitrifying  bacteria  .  46^17 

relation  of  blueberry  fungus 48-50 

determinations  in  kalmia  peat 45, 46 

( irganic,  used  by  fungi 48 

tubercles,  development  on  alfalfa  roots 16-17 

Noncalcareous  soil.    See  Soil,  noncalcareous. 
Normal  solution.     See  Solution,  normal. 

North  Carolina,  blueberries  in  Boston  market 12 

Nova  Scotia,  blueberries  in  Boston  market 12 

Nutrient  solution.    See  Solution,  nutrient. 

Nutrition  of  the  blueberry,  theory 50 

peculiarities  of  the  blueberry 40-50 

Oak  leaves  and  oak-leaf  mold.     See  Leaves,  oak. 

n  K  it  mycorrhiza,  description 44 

roots,  acidity  test 61-62 

sandy  woods,  presence  of  peal  suitable  to  blueberry 32-35 

Ohio,  absence  of  blueberry  and  related  plant  in  lirrvestone  scJirs 19 

(  Hiver,  G.  W..  method  of  germinating  blueberry  seeds 14,  51 

(  hob  ids.  use  of  Mai  via  nd  peal  in  growing 32 

Oregon,  title  swamps,  alkaline  character  of  peat 32 

Organic  matter.     Set  Matter,  cellular  and  organic. 

nitrogen.     See  Nitrogen,  organic. 
Outdoor  plants.     See  Plants,  outdoor. 
Oxid,  calcium.     See  Calcium  oxid. 

Oxycoccus  oxycoccus,  rool  fun  mis.  study 49 

Pacific,  humid  coast  sections,  occurrence  of  blueberry  and  related  plants 30 

Parent  plant.     No    Plant,  parent. 

Patterson,  Mrs.  V.  \\ . .  identification  of  blueberry  mildew -        79 

Peal,  acidity,  causes  and  characteristics 31-35,  61-62 

alkaline,  not  suited  for  growing  blueberry 32 

bacterial  content,  comparison  with  cow  manure 64 

bog.     See  r>o'_r.  peat. 

favorite  type  of  acid  soil  for  blueberry '^i~?~ 

fibrous  dial i led.  aeration  conditions  satisfactory  for  blueberry 37-38 

fresh,  effect  on  field  growth  of  blueberry 87 

excessi  ve  acidity ~f 

kalmia,  description,  process  of  formation 32-34 

determinations  of  nitrogen  and  nitrates 45,46 

extract  ion  of  humus 47 

moist ure  conditions 37-38 

nitrification  not  hiking  place 46,  47 

roots,  acidity  test 61-62 

p.-:; 


INDEX.  97 

aixture,  experiments  with  roses,  alfalfa,  and  blueberries.  .    .    15  r 

for  potting  plains 

the  bog  type,  suitability  for  blueberry  culture.. 

pure,  largesl  plants  grown  by  use.         ..........  ...        69 

suitabl  berry,  Bources. .  32 

upland,  definition 

I  in  pot  cultures,  discussion  .  52, 5-1  56,60  62 

water.  Set  Water,  peal 
Peaty  Boils.  Set  Soil,  peaty. 
Peculiarities  of  blueberry.    See  Blueberry,  peculiarities 

Peeling,  bark  of  blueberry 84 

Penicillin m  glaucum,  nitrogen  fixation lit 

yrlvania,  blueberries  in  Boston  market 12 

Phenolphthalein,  use  in  testing  soil  acidity 22 

I'h a,  occurrence  on  roots  of  plants  related  to  the  blueberry 

omitrium  imm  currence  on  alkaline  leaf  mold 

Physiological  dryne         v      Dryness,  physiological. 

Picking,  methods  in  use  with  blueberry 13-14 

Pine  branches.    Set  Branches,  pine. 

!  esenci  of  peat  suitable  to  blueberrj  32,34 

Pitcher  planl-.      Set    Plants,  pitchi 

Pith  of  blueberry  twigs  gorged  with  starch. .  ?6 

Plain,  Atlantic  Coastal,  occurrence  of  blueberries  and  related  plants 30,37 

Plant,  parent,  of  cultivated  seedlings 

Plants,  bog,  niti  milation,  methods. 50 

occurrence  on  sandy  upland  :i.r> 

preservation  from  decaj  31    >2 

dormant,  erratic  starting  when  wintered  ind -s 

use  in  field  plantings 

heath,  repotting  directions 70 

on i door,  compared  with  indoor  plants 7  1-75 

pitcher,  insect  food  for  supply  of  nitrogen 50 

Plumpness,  importance  as  market  feature 12 

Plunging,  use  of  method 15,65  67,  67-68,68-70 

Poifi us  character  of  acid  soils       Si  -  Soil,  acid 

Pollination,  blueberry 76 

Polycodium  stamineum,  reproduction  bj  rootstock  cuttings 86 

ilture.     See  <  lulture,  pot. 

lass,  use  in  blueberry  experiments 14, 15 

plunging,  advantages' 15,  ( 

thumb,  use  for  seedlin  trison  with  Hats 

Potting,  method  with  seedlings  of  five  months  59  62 

ol  blueberries 12,81 

Propagation,  blueberry,  discussion  of  methods 

Pruning  blueberry,  relation  to  method  of  laying  down  buds 71   72 

Purpling  of  blueberry  leaves,  occurrence,  causes,  etc  .   .  17,25,28 

Hake,  use  for  picking  blueberry 13 

Raj  b,  medullar} .  gorged  with  starch  in  blueberrj  twigs. .  76 

pider.     Se<  Spidei    red 

Repot  ting,  in  spring 67— < 

Set  also  Transplanting. 
Resting  spores     -s"  Spores,  resting 

Rhode  (stand,  experiments  in  blueberrj  culture II 

Ripening,  fruit,  description 
Rool  gi  uting      Set  Grafl 

growth.     Set  <  Irow  th,  root 
hair-      St '  I  fairs,  root . 

Rootlets,  blueberry  and  other  plants,  description 40   12 

Rool  ,  blueberrv,  growth  under  various  conditions  15, 17  21 

in  peat,  acidity  determination I 

inhabited  bj  a  mycorrhizal  fungus 42,  15 

use  of  cuttings  in  propagation 

Rootstocks,  blueberry,  propagation  of  blueberry  and  related  plants -so 

54708°— Bui    193     10         7 


98  EXPERIMENTS    IN    BLUEBERRY  CULTURE. 

Pago. 

Rose,  culture  in  garden  soil  and  in  peal 14, 15-16,  29 

Rosemary,  marsh,  root  fungus,  study 4!) 

Rotting  of  peat  in  blueberry  culture 34,52,56,60-61,87-88 

Sand,  use  in  field  plantings 88 

pot  cultures 25, 28,  52,  54,  60-(i  L,  66 

Sandstone,  broken  pieces,  use  in  soil  for  repotting  heath  plants 69  70 

Sandy  soil.     See  Soil,  sandy. 

woods.     See  Woods,  sandy. 

Sarracenia,  insect  food  for  supply  of  nitrogen :>o 

Saturation,  soil,  effect  on  blueberry  growth 35-36 

Schott,  Arthur,  on  shrubs  in  Smithsonian  grounds 11 

Scirpus  occidentalis,  forming  an  alkaline  peat 32 

Seed  flats.    See  Flats,  use  for  seedlings. 

Seedlings,  blueberry,  transplanting  details 15,  54-57,  59-60.  67,  88 

Seeds,  blueberry,  description  and  care 13, 51-54 

germination 14,51,53 

Selection,  use  in  improvement  of  blueberries 80,  82 

Shade,  effect  on  growth  of  plants 55,  56,  67-68,  70-71,  88 

Shipping,  adaptation  of  the  blueberry 13 

Shoots,  basal,  development 57,  58 

Smithsonian  Institution,  blueberry  bushes  in  grounds 11 

Soil,  acid,  poisonous  character 45, 50 

preference  of  blueberry  and  related  plants 15, 17, 19,  26,  28-30, 31-32 

acidity  tests 22, 26-28 

alkaline,  deleterious  to  blueberry  plants 26-31 

phenolphthalein  test,  discussion  and  directions 26-28 

bacteria.    See  Bacteria. 

blueberry,  deleterious  to  roses  and  alfalfa 15-17 

calcareous,  absence  of  blueberries  and  related  plants 19 

clay,  effect  on  growth  of  blueberry 24 

freshly  chopped,  deleterious  to  growth  of  blueberries 87 

garden,  not  suited  to  blueberry  cultivation 11,  14-17 

Kentucky  limestone,  absence  of  blueberry  and  related  plants 19 

limed,  unfavorable  to  the  blueberry 19-23 

mixtures  used  in  pot  cultures 25,  52,  54,  59  62 

moisture  measurement 37  38 

muck,  loss  of  acidity  by  drainage 35 

neutral,  deleterious  to  blueberry  plants 26  31 

noncalcareous,  occurrence  of  blueberry  and  related  plants 19,  30 

peaty,  acid,  deficiency  in  available  nitrogen 45-46 

requirements  of  the  blueberry 11,11    Hi 

rich,  absence  of  blueberry  and  related  plants 14-17, 17-19,  30 

sandy,  aeration  conditions  satisfactory  for  blueberry 36-37 

water-saturated,  deleterious  to  blueberry  growth 35-36 

See  also  Loam. 

Solution,  acid  and  alkaline,  effect  on  growth  of  blueberrj .  experiments 28-29 

acidity  determination 26  28 

normal,  definition 27 

nutrient,  acid  and  alkaline,  effect  on  growth  of  blueberry 28  -"-1 

Sowing,  seed  of  blueberry,  directions 51-52 

Sphagnum  moss.     See  Moss,  sphagnum. 

Spider,  red,  occurrence  and  control 55,  79-80 

Spores,  injurious,  found  in  mots  of  feeble  blueberrj  plants 64  65 

rest  ing,  Asterocystis  radicis 65 

Spring  beauty,  soil  not  good  for  blueberry 24 

Stagnation,  leaf  rudiment 28,  29,  55-56,  60 

Stamens  of  the  blueberry l^~V*. 

March  in  blueberry  twig's,  transformation,  etc 75  76 

Starvation,  danger" to  blueberry  from  lack  of  nitrates  in  soil 45-46,50 

Stations,  agricultural  experiment,  attempts  at  blueberry  culture 11 

Stem  gro'vt  th.     Se<  <  Irowth,  stem. 

«  ithering  at  tip,  cause  and  prevention 28,55-56,  60,  70,  71 

Stigma  of  the  blueberry 77-78 

Stone,  broken,  use  in  soil  for  reporting  heath  plants 69-70 

Subalpine blueberry.    Set  Blueberry,  subalpine 
Sugar-maple  woods,     S&  Woods,  sugar-maple. 
lit:: 


IM'IA.  99 

Sundews,  insecl  I I  for  supply  of  aitrogeu 50 

Swamp  blueberry.     Set   Blueberry,  swamp. 
Swarm  sp  in        v     Spores,  injurious 

rareonemus,  mite  infesting  the  blueberry 30 

rature  during  pot-culture  experiments 53, 55,  57 

absence  of  blueberry  and  related  plants  in  limestone  soils. ...  1!) 

Termination  of  stem  growth 58  59 

Ternetz,  Charlotte  on  mycorrhizal  fungi ii 

nychus  bimaculatus.    Set  Spider,  red. 

Theory  of  nutrition,  blueberry 50 

Thumb  pol        i      Pots,  thumb 

Transpiration,  bog  plants                                       againsl  poison  in  soil 50 

planting,  possibility,  erroneous  popular  idea II 

details 15, 

itl     l    ■    ,  determinations  of  nitrogen  in  kalmia  peat 15 

Trillium,  soil  not  Lr 1  for  blueberry 24,  34 

Tubercles,  nitrogen,  development  on  alfalfa  roots 16  17 

Tule,  forming  an  alkaline  peat 32 

Tu  ig  grow  ih.    See  Grow  th,  twig 

,  blueberry  plan!,  growth  stoppage  in  early  summer 0 

winter,  starch                large "(i 

i  pl.mil  peal      >      Peat    upland. 

I  plain  Is.  sandy,  occurrence  of  bog  plants,  causes 

Utricularia,  insecl  t 1  forsupplj  of  nitrogi  n 

I   in  in  oenum,  relation  to  V.  corymbosum 82 

atrococcum  forcing  for  flowering  buds,  experiment 72 

germination  of  s<  eds 53 

in  Smithsonian  grounds II 

laying  down  of  flowering  buds 7:; 

relation  to  V.  corymbosum 82 

September  too  late  for  budding 8  I 

stoppage  of  twig  growth 70 

canadense,  sourness  of  berry 8] 

corj  in  I '"-nil  i,  experiments  made  principally  with  this  species II 

parent  plant .  description 80  82 

related  to  A    atr :cum  1 1 

variability 81. 82 

fuscatum,  identification  of  plant II 

membranaceum,  produced  largi  st  berry II 

pallidum,  germination  of  seeds 

laying  down  of  flowering  buds 73 

relation  to  V   corj  mbosum 82 

use  in  budding 83 

pennsylvanicum,  fancy  price  for  early  heme- ....  gl 

relation  to  possible  blueberry  hybrid 82 

reproduction  by  root-stock  cuttings S(j 

sweet  ness  of  berry 81 

vacillans,  mildew  abundant  on 79 

vitisidaea,  root  fungus,  study in 

Variation,  swamp  blueberry  seedlings R2 

Varieties,  blui  bern .  valuable,  prospects 

Ventilation,  control,  for  blueberries 52,  55 

Wankinco,  cranberry  bog  near  Wareham,  Mass  .  growth  of  blueberry 

Wareham,  Mass.,  growth  of  blueberries  in  cranberry  bog  3(i 

brown  color  due  to  acid  humus r, 

content      Set  Moss,  sphagnum,  and  Soil,  moisture  measurement. 

cull ure.     See  Culture,  v 

level.     v     Bog    blueberry,  water  level 

acidity ....  2s 

satisfactory  nutritn  e  material  in  sand  cultures 

source  of  nourishment  tobogbluebi              40 

saturation  of  soil  injurious  to  growth  of  blueberry 

Watering,  excessive,  injurious  to  potted  blueberries. . 
infrequent  for  plunged  pots 
L93 


100  EXPERIMENTS    IX    BLUEBERRY    CULTURE. 

.  '  Page. 

i  ingof  blueberries  in  pots 55 

eeed  bed 52 

Wheat,  description  of  root  hairs 40-41 

Winter,  effect  on  young  plants 74-76 

Withering,  stem  tips,  cause  and  prevention 55-56 

occurrence 28.  60,  70,  7 1 

Woods,  sandy,  oak  or  pine,  source  of  peat  suitable  for  blueberry 32-:J,5 

sugar-maple,  rotting  of  leaves 84 

Worms,  thousand-legged,  hastening  decomposition  of  leaves :; 

S&  also  Earthworms. 

193 

O 


[Continued  from  page  '2  of  cover.] 

No.  107.  American  Root  Drugs.     1907.     Price,   15  cents. 

108  The  Cold   N  to  rag Small    Fruits.      1907.      I'rlce,    I  .">  cents. 

100.  American  Varieties  of  Garden  Beans.     Hhit.     Price,  25  cents. 

111).  Cranberry    Diseases       1907,      Price,   20  <  •nl  s. 

112.  Use  "i  Suprarenal  Glands  in  Testing  Drug  Plants.      1007.     Price,  10  cents, 

113,  Comparative  Tolerance  ol  Plants  for  Bnlts  In    Vlkall  s<dis.      1907.     Price;  15 
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117.  The  Reseedlng  ol   Depicted   Range  and   Native   Pastures.      L907.     Price,   lo  cents. 

us.   Peruvian  Alfalfa.      1007.     Price,  1 nis. 

119    The  Mulberry  and  Other  Silkworm-Food  Plants       1907,     Price,  10  cents. 
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125.  Drj  Land  Olive  Culture  in  Northern  Africa       1908      Price,  10  cents 

126.  Nomenclature  of  the  Pear.      1908      Price,  30  cents. 

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128.  Egyptian  Cdttou  In  the  Southwestern  United  States.      1908.     Price,  15  cots 

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130  Dry  Land  Agriculture       1908.     Price,  10  cents. 

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137.  Seeds  and  Plants  Imported,      Inventory  No:  14,      1909,      Price,  (0  cents. 

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159  Local    Adjustment  of  Cotton  Varieties.     1909.     Price,  Hi  cuts. 

160  Italian  Lemons  and  Their  By-Products,      L909.      Price,   15  cents. 

161  A  New  Type  of  Indian  Corn  from  China.      1910.     Price,  1"  cents. 

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n;i     Promising  Rool  tirops  for  the  South.      L910.      Price,  in  cents.  . 

165  Application  of  Principles  of  Heredity'  to  Planl  Breeding.     1910.     Price,  L0  cents. 

166  The  Mistletoe  Pesl  in  the  Southwest,      1910.     Price,  10  cents. 
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168  Seeds  and  Plants  Imported      Inventory  No,  19.     1909.     Price,  5  cents. 
[69  Variegated  Alfalfa.      1010:      Price.'  10  cents. 

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178.  Improvement  of  the  Wheat  Crop  of  California,      mm.     Price,  10  cents. 

179.  The  Florida  Velvet  Bean  and  Related  Plants      1910.     Price,  10  cents. 

180  Agricultural  and  Botanical  Explorations  In  Palestine,     l'.nn.     Price,  15  cents. 

181  Tne  Curly  Top  of  Beets.     1910.     Price,   15  cents. 

182.  i  Experienci    with  the  Swedish  Select  Oat     1910.     Price,  10  cents. 

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i :.  c 

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188    Dry  Farming  in  Relation  to  Kami. ill  and  Evaporation.      [In  press.] 

180    Soun f  the  Drug  Dloscorea,  with  a  Consideration  of  the  Dloscorea?  Found  in  the 

I  nlted  Stat<  b      I  In  press,  I 

190.  Orchard  Green  Manure  Crops  in  California,      I  in  press.] 

191.  val f  Plrsl  Generation  Hybrids  in  Corn.      I  in  press.] 

r.i_'.  Drought  Realstan* i  the  Olive  In  the  Southwestern  States.     I  in  press.] 

198 


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